CN1778121A - Method and apparatus for enhanced coding in a multi-user communication system - Google Patents

Abstract

The first and second sets of information are transmitted using a relatively large transmission block comprising a plurality of Minimum Transmission Units (MTUs), wherein each MTU corresponds to a unique combination of resources. A first set of the MTUs is used to convey the first set of information, the first set of MUTs including at least a majority of the MTUs in a transport block. Defining, e.g., selecting, a second set of said MTUs for communicating said second set of information, said second set of MTUs comprising fewer MTUs than the first set and at least some MTUs being comprised in the first set. The first and second sets of information are communicated by transmitting at least some of the MTUs included in the first and second sets of MTUs with corresponding information modulated thereon. The information may be communicated by superimposing the first and second information on a common MTU.

Description

Method and apparatus for enhanced coding in a multi-user communication system

technical field

The present invention is directed to improved methods of encoding and transmitting information in wireless communication systems.

Background technique

Superposition coding in a multi-user communication system will now be discussed. A multi-user communication system includes several transmitters and receivers communicating with each other and may use one or more communication methods. In general, multi-user communication methods can be classified into one of two cases:

(a) a single transmitter communicates with several receivers, which is commonly referred to as a broadcast communication method, and

(b) Several transmitters communicate with one common receiver, which is generally called a multi-access communication method.

Broadcast communication methods are often referred to as "broadcast channels" in communication and information theory literature, and will be referred to as such in the remainder of this document. The "broadcast channel" refers to the physical communication channel between a transmitter and multiple receivers and the communication resource used by the transmitter to communicate. Similarly, multiple access communication methods are commonly referred to as "multiple access channels" and the remainder of this document will use this term. Likewise, the "multiple access channel" refers to a physical communication channel between multiple transmitters and a common receiver, as well as communication resources used by the transmitters. A broadcast communication method is often used to implement a downlink communication channel in a typical cellular wireless system, in which a base station broadcasts to a plurality of wireless terminals, while an uplink channel in such a system is usually implemented using a multiple access communication method, Wherein multiple wireless terminals can transmit signaling to one base station.

Transmission resources in a multi-user communication system can usually be expressed in time, frequency or code space. Information theory shows that, in particular, in the same transmission resource, e.g. simultaneously in the same frequency, by simultaneously transmitting to multiple receivers in the case of broadcast communication methods, or by allowing multiple The transmitters transmit simultaneously, in both cases increasing the capacity of the system. In the case of broadcast communication methods, the technique for simultaneous transmission to multiple users in the same transmission resource is also referred to as "superposition coding". In the context of the present invention, controlled superposition coding appears to be a valuable practical technique in both broadcast and multiple access communication methods.

The advantages of superposition coding will be apparent in view of the following discussion of transmission techniques used in broadcast communication methods. Consider a single transmitter communicating with two receivers, their channels can be described by ambient Gaussian noise levels _N1 and _N2 , where _N1 < _N2 , i.e. the first receiver has a stronger Channel. Assume that the communication resources available to the transmitter are total bandwidth W, and total power P. A transmitter can employ several strategies to communicate with a receiver. Figure 1 includes a graph 100 depicting the speeds achievable in a broadcast channel by a first user with a stronger receiver and a second user with a weaker receiver under three different transmission strategies. The vertical axis 102 of FIG. 1 represents the speed of stronger receivers, while the horizontal axis 104 represents the speed of weaker receivers.

First, consider a strategy in which the transmitter multiplexes between two receivers in time, allocating all of its resources to one receiver at a time. If the fraction of time spent communicating with the first (stronger) receiver is denoted by α, it is not difficult to prove that the attainable speed of two users satisfies

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="A20048001043900421.png,A20048001043900461.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="A20048001043900421.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

The speed achieved by the above formula is represented by the line 106 in FIG. 1 representing the time division multiplexing (TDM) strategy as a function of the time fraction a taken to serve the first user. Now consider another transmission strategy, where the transmitter allocates some portion of the bandwidth, β, and a portion of the available power, γ, to the first user. The second user gets the remainder of the bandwidth and power. After allocating these parts, the transmitter communicates with both receivers simultaneously. Under this launch strategy, the characteristics of the velocity region can be expressed by the following formula.

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="A20048001043900421.png,A20048001043900461.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;P</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="A20048001043900421.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

The speed achieved by the above formula can be seen intuitively from the raised segmented curve 108 in FIG. 1 representing the frequency division multiplexing (FDM) strategy. It is clear that the strategy of allocating the available power and bandwidth between the two users in an appropriate manner trumps the temporal separation of resources. However, the second strategy is still not optimal.

The supremum of the speed region achievable under all launch strategies is the broadcast capacity region. For the case of Gaussian noise level, the region is characterized by the formula

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="A20048001043900421.png,A20048001043900461.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;P</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="A20048001043900421.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; W</span>}\mathrm{<span\; class="notranslate">\; log</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;P</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

, and is depicted by the dashed curve 110 in FIG. 1 representing capacity. It was pointed out by Thomas Cover in IT-18(1):214, 1972, IEEE Transactions on Information Theory, Broadcast Channels, T.M. Cover, that a communication technique called superposition coding can reach this capacity region. In this technique, signals to different users are transmitted using different powers superimposed on each other in the same transmission resource. The gain achievable by superposition coding exceeds that of any other communication technique that requires sharing of transmission resources among different users.

The basic concept of superposition coding is shown in graph 200 of FIG. 2 . Graph 200 includes a vertical axis 202 representing quadrature and a horizontal axis 204 representing in-phase. Although this example uses QPSK modulation, in general the choice of modulation settings is not limited. Also, this example outlines the case of two users, but the concept can be generalized to multiple users in an easy way. Assume that the total transmit power budget of the transmitter is P. Assume that a first receiver, called the "weaker receiver", has greater channel noise, and a second receiver, called the "stronger receiver", has less channel noise. The four pattern-filled circles 205 represent QPSK constellation points that will be transmitted at high power (better protected), (1-α)P, to weaker receivers, where arrows 206 provide an indication of the high power QPSK transmission strength. Measurement. At the same time, the QPSK constellation is also used to convey additional information to stronger receivers at a low power (less protected), αP, where arrow 207 provides a measure of the lower power QPSK transmission strength. The actual transmitted symbols combining the two high-power and low-power signals are represented as blank circles 208 in FIG. 2 . The key concept represented by this illustration is that the transmitter communicates with both users simultaneously using the same transmit resources. In this document, high power signals are also referred to as protected signals, and low power signals are also referred to as regular signals.

The receiver's strategy is fairly simple. A weaker receiver observes a high power QPSK constellation with a low power signal superimposed on it. When a weaker receiver decodes a high power signal, the signal-to-noise ratio (SNR) perceived by the weaker receiver may not be sufficient to analyze the low power signal, so the low power signal appears as noise and slightly degrades the SNR. On the other hand, the SNR perceived by stronger receivers is sufficient to analyze both high-power and low-power QPSK constellation points. The strategy of the stronger receiver is to first decode the high power points (which are intended for the weaker receiver), remove their influence from the composite signal, and then decode the low power signal.

In practice, however, this strategy often doesn't work very well. Any imperfections in the removal of the high-power signal appear as noise to the decoder recovering the low-power signal.

In view of the foregoing discussion, it is apparent that there is a need for novel methods and apparatus that allow communication systems to operate using controlled superposition coding broadcast and/or multiple access communication methods to take advantage of the higher speeds achievable in the channel , while overcoming the practical difficulties of imperfectly canceling high-power signals and the complexity and cost associated with the joint decoder approach.

Contents of the invention

The present invention is directed to transmitter and receiver techniques for encoding that enable decoding of regular signals without being compromised by imperfect cancellation of protected signals.

Exemplary embodiments of the present invention are described below in the context of a cellular wireless data communication system using Orthogonal Frequency Division Multiplexing (OFDM). Although a typical wireless system is used for the purpose of explaining the invention, the invention is not limited to the exemplary embodiment, and can also be applied to many other communication systems, such as those using Code Division Multiple Access (CDMA).

According to various embodiments of the present invention, the first and second sets of information are transmitted using one transport block, said transport block comprising a plurality of minimum transmission units, each minimum transmission unit corresponding to a unique combination of resources, said resources comprising time , frequency, phase and at least two of spreading codes. The smallest transfer unit is also called a degree of freedom. In this document, the terms minimum transfer unit and degrees of freedom are used interchangeably. A transport block may be relatively large when compared to the smallest size transport block that may be required to encode one of the sets of information to be transmitted.

An exemplary embodiment of the present invention includes defining a first set of said minimum transmission units for conveying said first set of information, said first set of minimum transmission units comprising at least the size of the minimum transmission units in said transport block part, defining a second group of said minimum transmission units for conveying said second group of information, said second group of minimum transmission units comprising fewer minimum transmission units than the first group; the first and second groups At least some of the minimum transmission units are the same; and the first and second sets of information are communicated using minimum transmission units contained in said first and second sets of minimum transmission units. A first set of said minimum transmission units contained in a transport block is used to convey said first set of information, said first set of minimum transmission units comprising at least a majority of said minimum transmission units in a transport block. defining, for example, selecting a second group of said minimum transmission units for communicating said second group of information, said second group of minimum transmission units comprising fewer minimum transmission units than the first group; first and second At least some of the minimum transmission units in the group of minimum transmission units are identical. The first and second sets of information are communicated by transmitting at least some of the smallest transmission units comprised in said first and second sets of smallest transmission units with corresponding information modulated thereon. Information can be transmitted by superimposing the first and second information on the shared minimum transmission unit, or by breaking down the first group of information so as to transmit the second group of information on the first and second shared minimum information unit. Error correcting codes can be used to recover information lost due to superimposition of the second set of information on the common transmission unit. The information transmitted in the first and second set of information may be, for example, user data and control information including acknowledgments and assignments.

The first and second sets of information may, and in various embodiments are, be transmitted using the first and second portions of the minimum transmission unit by transmitting from different transmitters minimum transmission units comprising modulation information corresponding to different sets of information . The transmitter may be located in a different device such as a wireless terminal. In other embodiments, the first and second sets of information are communicated by transmitting the smallest transmission unit used to communicate the first and second sets of information from a single transmitter, such as a base station transmitter.

The first set of minimum transmission units comprises a majority of the minimum transmission units in the transport block, but typically a higher proportion of the minimum transmission units, e.g. in some embodiments the first set of minimum transmission units comprises at least 75 of the total number of minimum transmission units %, and sometimes, including 100% of the smallest transmission unit in the block. The second set of minimum transmission units usually comprises less than 50% of the minimum transmission units in a block, and sometimes relatively few minimum transmission units, for example less than 5 or 10% of the number of minimum transmission units in a transport block. In this case, even if a receiver attempting to decode the smallest transmission unit used to convey the first set of information does not recover any of the second set of transmission units, by using an error-correcting code in some embodiments, it may The information of the first group intended to be transmitted on some of the smallest transmission units comprised in the second group is recovered.

By using a minimum transmission unit common to both the first and the second set of minimum transmission units, correct superposition can be used to convey information corresponding to both the first and the second set of information. Alternatively, the information corresponding to the first set of information intended to be transmitted on the common smallest information unit can be punctured (eg not transmitted), while the punctured information can be recovered by using an error correction code.

In a particular exemplary embodiment, said first and second sets of information using at least some of the minimum transmission units comprised in the first set of minimum transmission units may be transmitted at a first power level as part of the transmission process, The minimum transmission units of the second set of minimum transmission units are simultaneously transmitted using a higher power level on a per minimum transmission unit basis than the first signal. The smallest information unit of said second set is transmitted at a power level which, in some embodiments, is at least 3dB greater than the power level at which the smallest transmission unit corresponding to the first signal is transmitted. It is sometimes possible, and indeed, to vary the power level of the smallest information unit in said first and second groups, for example to reflect changes in channel conditions.

Various receiver embodiments are possible according to the invention. Two receivers, eg a first and a second receiver, can operate independently and in parallel. From the smallest information unit in said transport block actually transmitted, one receiver is used to recover the first set of information and the other receiver is used to recover the second set of information. In one such embodiment, the first receiver considers the smallest information block comprising a signal corresponding to the second set of information as comprising impulse noise and eg discards, ignores or minimizes their impact on the output of the receiver. In such an embodiment, the second receiver considers the influence of the received signal of the smallest transmission unit corresponding to the first set of information as background noise. Since the signal corresponding to the second set of information is usually transmitted using a relatively high power level, such as a power level sufficient for the first receiver to perceive the signal as impulsive noise, even when the signal corresponding to the first set of information It is also generally relatively easy to recover the second signal in the presence of background noise. Since the impact of transmitting the second set of information is usually limited to relatively few symbols in the transport block, the impact of high power signals on the signal used to transmit the first set of information tends to be very localized, allowing in most cases to be achieved by using Traditional error-correcting codes in the transmitter message, recovering any lost information.

In another embodiment of the invention, an apparatus also includes two receivers. However, instead of operating independently and in parallel, the first receiver identifies the minimum transmission unit corresponding to the second set of information, eg a high power minimum transmission unit. It then passes to the second receiver information indicating which received smallest transmission unit corresponds to the second set of information. The second receiver discards the minimum transmission unit corresponding to the second group of information, and then decodes the remaining received minimum transmission units. Since the number of discarded minimum information units tends to be small, for example below 5% of received minimum information units in most cases, the second receiver avoids loss due to minimum transmission units during transmission by using The error-correcting codes that cause errors due to corruption or corruption can usually still recover the complete first set of information.

In various embodiments, the present invention realizes the benefits of superposition coding in a multi-user communication system while using a receiver that is simple in design but still performs well in terms of performance. The present invention discloses a novel and efficient superposition coding technique for both broadcast and multiple access channels.

In the case of a broadcast channel, for example, a single transmitter sends data to multiple receivers. In the context of a typical system, the transmitter is a base station that communicates with a wireless receiver, such as a mobile receiver, in a cellular downlink. A mobile user in a cellular system may experience various SNR states due to variations in path loss according to location within a cell. Without loss of generality assume that the base station has two signals that it wants to communicate simultaneously with two different mobile receivers that experience different path losses. Regular signals are intended for receivers that experience a higher signal-to-noise ratio (SNR), hereinafter referred to as "stronger" receivers. The second signal, termed the "protected" signal, is intended for use by "weaker" receivers operating at lower SNRs on lower quality channels. The classification of mobile receivers as "stronger" or "weaker" is not static but a relative definition.

If superposition coding is not used, the air link resources should be allocated between regular and protected signals, which is not optimal. In order to distinguish the new method of superposition coding disclosed in the present invention, the existing method of superposition coding described in the background section is hereafter referred to as "traditional superposition coding" in the remainder of this document. In a traditional superposition coding environment, both protected and regular signals are transmitted using the same air-link resources. For example, assume that the air link resource for simultaneous transmission of regular and protected codewords includes K symbols, A ₁ , . . . , A _K . Also assume that a regular codeword will convey M information bits and a protected codeword will convey N information bits. It is assumed that both regular and protected codewords use BPSK (Binary Phase Shift Keying) modulation. In traditional superposition coding, M regular information bits are converted into K coded bits by a coding scheme such as convolutional coding, and then these K coded bits are mapped to K BPSK symbols B ₁ , ..., B _K . At the same time, through another coding scheme such as convolutional coding, the N protected information bits are converted into different K coded bits, and then these K coded bits are mapped to K BPSK symbols C ₁ , ..., C _K . Finally, combine K BPSK symbols from protected information bits and K BPSK symbols from regular information bits, and use K air link resource symbols A ₁ , ..., A _K : A ₁ =B ₁ + C ₁ , . . . , A _K = B _K + C _K emit it. In composite signals, the protected symbols are usually transmitted with higher power per bit so that weaker receivers can receive them reliably. Conventional symbols are transmitted with relatively low power per bit. In this example, and in general terms in nature, the energy of the conventional signal is distributed among all the degrees of freedom over which the protected signal will be emitted.

The power of the transmitter is chosen in such a way that weaker receivers are generally only able to decode protected codewords. To the receiver, the normal signal appears only as noise. On the other hand, stronger receivers should be able to decode both codewords. A good decoding strategy that a stronger receiver can employ is to try to decode the two codewords together. However, this is often too complex for a practical receiver. Therefore, the strategy usually adopted by stronger receivers is sequential decoding. Stronger receivers first decode the protected codeword, then remove it from the received composite signal, and finally decode the regular codeword, which is the meaningful codeword for the stronger receiver. In practice, however, the above sequential cancellation and decoding schemes cannot always be performed well. If the SNRs of the stronger and weaker receivers and the required speed of communication are such that the normal and superimposed signals are transmitted with approximately the same power, then it may be difficult or inaccurate to eliminate the protected codewords.

In fact, even when the transmitted powers on the two codewords are different, there is an impediment to sequential decoding. For example, most communication systems experience some degree of inherent noise at the receiver. Unlike additive noise, this inherent noise is generally associated with the transmitted signal and has energy proportional to the transmitted power. Channel estimation noise in a wireless communication system is an example of inherent noise. In the context of conventional superposition coding, channel estimation noise causes imperfect cancellation of the protected signal at stronger receivers. The residual canceled errors may have considerable energy, especially when compared to the low power summed signal. Therefore, stronger receivers may not be able to correctly decode conventional codewords in view of residual cancellation errors.

From the discussion, it is clear that while traditional superposition coding distributes the energy of the protected codeword in each degree of freedom, it is desirable to concentrate this energy among one or a few degrees of freedom. According to the invention, focusing the energy over a limited number of degrees of freedom facilitates easy detection and cancellation of the protected signal at the receiver, even when the overall transmitted energy comprised in the two signals is similar. According to the invention, the energy in the codeword is concentrated between one or a few degrees of freedom.

Using the encoding and transmission methods described above, multiple sets of information may be transmitted using a common set of overlapping communication resources, such as time, frequency and/or code. Numerous additional features and benefits of the present invention will be apparent in view of the following detailed description.

Description of drawings

Figure 1 depicts a graph representing the achievable speeds in a broadcast channel for a first user with a stronger receiver and a second user with a weaker receiver for three different transmission strategies.

Fig. 2 shows an example of superposition coding using QPSK modulation.

Figure 3 shows an example of pulse position modulation.

Fig. 4 shows an example of high-speed superposition coding according to the present invention.

Fig. 5 shows another example of high speed superposition coding according to the present invention, in which the blinking signal concentrates its energy at 4 symbol positions.

Figure 6 shows a typical high speed superposition coding in a multiple access channel according to the present invention, represented as a composite signal at the base station receiver.

Figure 7 shows a typical traffic portion and the allocation of traffic portions to users by the base station.

Figure 8 shows a typical allocation section corresponding to a service section.

Figure 9 shows a typical downlink traffic section and acknowledgment section.

Figure 10 shows a typical allocation section, downlink traffic section and acknowledgment section, where both the allocation and acknowledgment sections use high speed superposition coding in accordance with the present invention.

Figure 11 shows 2 typical sets of messages, a transport block of a Minimum Transmission Unit (MTU) and partially overlapping sets of MTUs, which may be used to define groups of messages and may be used in part or in whole to transmit signals to convey information, in accordance with the present invention .

Fig. 12 shows a transport block of another typical MTU according to the present invention, which shows that the transport block can be subdivided into sub-blocks.

Fig. 13 shows a method according to the invention of transmitting two signals corresponding to two sets of information using different devices having different transmitters each generating a signal corresponding to one set of information.

Figure 14 shows two other methods of transmitting two sets of information in accordance with the present invention, either using a single transmitter that outputs two signals, where each signal corresponds to information in one set of information, or using signaling that is combined internally to output A single transmitter for a single composite signal.

Figure 15 shows two devices according to the invention including filtering and an error correction module; each device includes two receivers and each device can be used to receive the composite signal and retrieve the two sets of information that have been transmitted.

Figure 16 shows another device according to the invention comprising an MTU signal identification module; said device comprises two receivers and said device can be used to receive the composite signal and retrieve the two sets of information that have been transmitted.

Figure 17 shows a typical communication system implementing the apparatus and method of the present invention.

Figure 18 shows a typical base station implemented in accordance with the present invention.

Figure 19 shows a typical terminal node (wireless terminal) implemented in accordance with the present invention.

Detailed ways

The present invention is directed to transmitter and receiver techniques for encoding that enable decoding of regular signals without being compromised by imperfect cancellation of protected signals.

FIG. 17 illustrates an exemplary communication system 1700 using apparatus and methods in accordance with the present invention. A typical communication system 1700 includes a plurality of base stations, including base station 1 (BS 1) 1702 and base station N (BS N) 1702'. The BS 11702 is connected to a plurality of End Nodes (EN), EN 11708, EN N 1710 via wireless links 1712, 1714, respectively. Similarly, BSN 1702' is connected to a plurality of end nodes (EN), EN 11708', EN N 1710' via wireless links 1712, 1714', respectively. Cell 11704 represents the wireless coverage area in which the BS 11702 can communicate with an EN, such as EN11708. Cell N 1706 represents the wireless coverage area over which the BSN 1702' can communicate with an EN, such as EN 11708'. EN 1708, 1710, 1708' and 1710' can move around in communication system 1700. Base stations BS 11702, BSN 1702' are connected to a network node 1716 via network links 1718, 1720, respectively. Network node 1716 is connected via network link 1722 to other network nodes, such as other base stations, routers, home agent nodes, Authentication Authorization Accounting (AAA) server nodes, etc., and to the Internet. Network links 1718, 1720, 1722 may be, for example, fiber optic cables. Network link 1722 provides an interface outside of communication system 1700 to allow users, such as ENs, to communicate with nodes outside of system 1700 .

Figure 18 shows a typical base station 1800 in accordance with the present invention. Exemplary base station 1800 may be a more detailed illustration of base station 1702, 1702' of FIG. A typical base station 1800 includes multiple receivers connected together via a bus 1826, Receiver 1 1802, Receiver N 1804, multiple transmitters, Transmitter 1 1810, Transmitter N 1814, a processor 1822 such as a CPU, an I /O interface 1824 and memory 1828 . Various units 1802 , 1804 , 1810 , 1814 , 1824 , and 1828 can exchange data and information via bus 1826 .

Receivers 1802, 1804 and transmitters 1810, 1814 are connected to antennas 1806, 1808 and 1818, 1820 respectively, thereby providing a path for base station 1800 to communicate with end nodes, such as wireless terminals, within its cellular coverage area, e.g. Exchange data and information. Each receiver 1802, 1804 may include a decoder 1803, 1805, respectively, to receive and decode signaling encoded and transmitted by an end node operating within its unit. The receivers 1802, 1804 may be any of the typical receivers shown in the device 51502 of FIG. 15, the device 61532 of FIG. 15, or the device 71562 of FIG. , 1538), (1563, 1564). In accordance with the present invention, receivers 1802, 1804 should be capable of receiving a composite signal comprising a regular or base signal and a flashing signal and retrieving the field corresponding to the original pre-transmitted field. Each transmitter 1810, 1814 may include an encoder 1812, 1816 to encode signaling prior to transmission. Transmitters 1810, 1814 may be any of the typical transmitters shown in devices 11302 and 21308 of FIG. 13, device 3 of FIG. 14, or device 41410 of FIG. (1404), (1412). In accordance with the present invention, the transmitters 1802, 1805 should be capable of transmitting one or more of the following: regular or base signal, flashing signal and/or composite signal.

Memory 1828 includes routines 1830 and data/information 1832 . Processor 1822 performs processing by executing routines 1830 in memory 1828 and controlling operation of base station 1800 using data/information 1832 in memory 1828 to operate receivers 1802, 1804, transmitter 1810, and I/O interface 1824 Controls basic base station functions, and controls and implements the new features and improvements of the present invention, including generating and transmitting composite signals, receiving composite signals, sorting composite signals into regular or basic signal information and flashing signal information, classifying and recovering information. I/O interface 1824 provides base station 1800 with an interface to the Internet and other network nodes, such as intermediate network nodes, routers, AAA server nodes, home agent nodes, etc., thereby allowing end nodes to communicate with base station 1800 over wireless links Connect, communicate and exchange data and information with other peer nodes, such as another terminal node, throughout the communication system and outside the communication system, eg via the Internet.

Routine 1830 includes communication routine 1834 , and base station control routine 1836 . Base station control routines 1836 include a scheduler 1838 , an error detection and correction module 1840 , a transmitter control routine 1844 and a receiver control routine 1846 . Data/information 1832 includes received information 11850, received information N 1852, transmitted information 1 1854, transmitted information N 1856, identified MTU information 1858, and user data/information 1848. User data/information 1848 includes a plurality of user information, user 1 information 1860 and user N information 1862 . Each user information, such as user 1 information 1860 , includes terminal identifier (ID) information 1864 , data 1866 , channel quality report information 1868 , partial information 1870 , and classification information 1872 .

Transmit Information 11854 may include a set of information that may correspond to a first signal, e.g., a regular or fundamental signal, information defining transport blocks that may be used to transmit the MTU of said first signal, defining the MTU that will be used to define said signal Information of a first set of MTUs on which to be modulated to define information of said first signal, information of which MTUs corresponding to information of the first signal should be transmitted to eg a wireless terminal. In some embodiments, each MTU conveying the first set of informational data will be transmitted. In other embodiments, most MTUs conveying the first set of information should be transmitted. In such an embodiment, prior to transmission, the MTU corresponding to the first set of information and simultaneously corresponding to the second set of information, eg, a flashing signal, may be discarded.

Transmit Information N 1856 may include a set of information that may correspond to a second signal, e.g., a flash signal, information defining a transport block that may be used, e.g., to transmit an MTU of said second signal to a wireless terminal, that will be used for Information defining a second set of MTUs of said second signal on which to modulate to define information of said second signal. Said first and second transport blocks may be identical. In such cases, transport block information specifying the size and/or shape of the common transport block from transmission information 1854, 1856, respectively, may be, and often is, stored in memory 1828. Received information 11850 includes a first set of information recovered from receiver 11802, eg, information corresponding to a first set of pre-transmission information for wireless terminals. The first set of recovered information may, for example, be recovered from conventional or base signals. Received information N 1852 includes a second set of information recovered from receiver N 1804, such as information corresponding to pre-transmission information for a second set of wireless terminals. The second set of recovered information may, for example, be recovered from flashing signals.

The regular and flashing signals that define each original pre-emission group share some common MTU. The identified MTU information 1858 may include a set of MTUs identified in the second or flash signal, the identified set of MTUs may be obtained by the decoder 1805 of the receiver N. The identified MTU information 1858 may be forwarded to the receiver 11802, where the receiver may exclude those MTUs before passing the received signal to execute the error correction module, or alternatively, the identified MTU information 1858 may be forwarded to an in-memory The error detection and correction module 1840 and/or the error detection and correction module in the decoder 1803 .

Data 1866 may include data received from end nodes and data to be transmitted to end nodes. In some embodiments, one terminal identifier ID 1864 is used for each of the N wireless terminals that can interact with the base station at the same point in time. When entering a cell, a wireless terminal, such as a terminal node, is assigned a terminal ID 1864. In this way, the terminal ID will be reused as the wireless terminal enters and leaves the cell. Each base station has a set of terminal identifiers (terminal IDs) 1864 assigned to users (eg, wireless terminals) to be served. Channel quality report information 1868 may include information about the user's channel quality judged by the base station 1800, and feedback information from the user including downlink channel quality reports, interference information, and power information from wireless terminals. Portion information 1870 may include according to usage type, such as traffic channel, assigned channel, request channel; characteristics, such as MTU, frequency/phase and time, OFDM tone symbol; signal type used for the part, such as regular or basic vs. flashing signal , to define the information for the section assigned to the user. Classification information 1872 includes information classifying users, eg, wireless terminals, as "stronger" or "weaker" transmitters.

Communication routines 1834 include various communication applications that may be used to provide special services, such as IP telephony services, text services, and/or interactive games, to one or more user end nodes in the system.

Base station control routines 1836 perform functions including basic base station control and controls related to the apparatus and methods of the present invention. Base station control routines 1836 exercise control of signal generation and reception, error detection and correction, data and pilot hopping sequences, I/O interface 1824, allocation of parts to users, and scheduling of users to terminal IDs 1864. More specifically, scheduler 1838 schedules users to terminal ID 1864, using user classification information 1872 and portion information 1870 to assign portions to users. According to the invention, the scheduler decides as to which user and which part should be allocated to the regular or basic signal, and which user and which part should be allocated to the flashing signal. Certain users, such as those who have high power available and will transmit small amounts of information, may be better suited for flashing signaling than others who may wish to transmit large amounts of information and have limited power available. Certain types of channels may be better suited for flashing signaling. For example, in many cellular communication systems, control channels are transmitted at broadcast power because they are bound by mobile users with the weakest channels. Blink signaling is well suited for this application, and its use can often result in a power reduction with little loss of robustness. By using the classification information 1872 and the part information 1870, the scheduler 1838 can match users with low downlink signal-to-noise ratios (SNR) to regular parts within the channel, while users with high SNR can be matched with the within-channel The flashing (eg "protected") portion of the .

In accordance with the present invention, transmitter control module 1844 uses data/information 1832 including transmit info 1 1854, transmit info N 1856, terminal ID 1864, data 1866, and partial info 1870 to generate transmit signals and control transmitters 1810, 1814 operation. For example, the transmitter control module 1844 may control the transmitter 1810, via its encoder 1812, to encode the groups of information included in the transmission information 1 1854 into a signal that the transmitter 1 1810 can transmit, such as a regular or base signal. Transmitter control module 1844 may use the MTU set corresponding to transmit information N 1856 to encode the set of information included in the information 1856 into a flashing or protected signal. Transmit Control Module 1844 may control Transmitter N 1814, via its Encoder 1816, to encode the groups of information included in Transmit Information N 1856 into a signal that Transmitter N 1814 may transmit. For example, transmit control module 1844 may use the MTU set corresponding to transmit information N 1856 to encode the set of information included in the information 1856 into a flashing or protected signal. Alternatively, in various embodiments of transmitters 1810, 1814, a single transmitter may be used that combines or mixes signals internally under the direction of transmitter control module 1844 according to transmit information 1 1854 and transmit information N 1856. Such mixing operations may include superimposing regular and flash signals prior to transmission, and/or selectively forming an MTU transmission that includes each flash signal cell and the cells in the regular signal not included in the flash signal Group.

In accordance with the present invention, receiver control module 1846 controls the operation of receivers 1802, 1804 to receive the composite signal and extract two sets of information, such as receiver information 1 1850 and receiver information N 1852. Receive processing under the control of the receiver control module 1846 may include controlling the decoders 1803, 1805, as well as controlling other units within the receiver. In some embodiments, the receiver control module 1846 controls the impulse noise filtering, background noise filtering, and error correction modules together with the receivers 1802, 1804. In some embodiments, the receiver control module controls the second signal MTU identifier module in one receiver, e.g., receiver N 1804, and the drop module in another receiver, e.g., receiver 1 1802 , and pass the identified MTU information 1858 from Receiver N 1804 to Receiver 1 1802; this allows Receiver 1 1802 to remove the MTU including the flashing signal information from the information stream entering the error detection module which attempts to recover the regular signal information group.

The error correction module 1840 operates in conjunction with or instead of an error detection and error correction module that may be included in the receivers 1802,1804. The error detection and correction capabilities included in receivers 1802, 1804 and/or module 1840 allow base station 1800 to reproduce a field corresponding to a pre-transmission field even if the (conventional or underlying) signal representing the pre-transmission field has been affected by the first The superposition of two flashing signals (flashing signal) or the phenomenon of breakdown caused by the second signal (flashing signal), for example, the effect of replacing some MTUs. In some embodiments, the MTU corresponding to the second set of information completely covers the MTU corresponding to the first set of information. Furthermore, in some embodiments, the MTU corresponding to the first set of information completely occupies one transport block.

Figure 19 shows a typical terminal node (wireless terminal) 1900 in accordance with the present invention. The exemplary terminal node 1900 may be used for any of the terminal nodes 1708, 1710, 1708', 1710' of FIG. A typical terminal node 1900, such as a wireless terminal, may be a mobile terminal, a mobile phone, a mobile node, a fixed wireless device, and the like. In this application, references to terminal node 1900 may be interpreted as corresponding to any wireless terminal, mobile node, or the like. A wireless terminal may be a mobile node or a stationary device supporting a wireless communication link. A typical end node 1900 includes multiple receivers connected together via a bus 1928, Receiver 1 1902, Receiver N 1904, multiple transmitters, Transmitter 1 1910, Transmitter N 1912, a processor 1926 such as a CPU, and Memory 1930. Through the bus 1928, the various units 1902, 1904, 1910, 1912, 1926, 1930 can exchange data and information.

Receivers 1902, 1904 and transmitters 1910, 1912 are connected to antennas 1906, 1908 and 1914, 1916, respectively, thereby providing a path for an end node, such as wireless terminal 1900, to base station 1800 within which the wireless terminal 1900 operates within the cellular coverage area To communicate, such as exchanging data and information. Each receiver 1902, 1904 may include a decoder 1918, 1920, respectively, to receive and decode signaling encoded and transmitted by the base station 1800. The receivers 1902, 1904 may be any of the typical receivers shown in the device 51502 of FIG. 15, the device 6 1532 of FIG. 15, or the device 7 1562 of FIG. (1536, 1538), (1563, 1564). In accordance with the present invention, receivers 1902, 1904 should be able to receive a composite signal comprising a regular or base signal and a flashing signal, and retrieve the field corresponding to the original pre-transmitted field. Each transmitter 1910, 1912 may include an encoder 1922, 1924 that encodes signaling prior to transmission. Transmitters 1910, 1912 may be any of the typical transmitters shown in Device 1 1302 and Device 2 1308 of FIG. 13, Device 3 of FIG. 14, or Device 4 1410 of FIG. 1310), (1404), (1412). In accordance with the present invention, the transmitters 1910, 1912 should be capable of transmitting one or more of the following: a regular or base signal, a flashing signal and/or a composite signal.

Memory 1930 includes routines 1932 and data/information 1934 . Processor 1926 performs the process of controlling the basic wireless by executing routines 1932 in memory 1930 and controlling the operation of end node 1900 using data/information 1934 in memory 1930 to operate receivers 1902, 1904 and transmitters 1910, 1912. Terminal functions, and control and implement the new features and improvements of the present invention, including generating and transmitting composite signals, receiving composite signals, sorting composite signals into regular or basic signal information and flashing signal information, classifying and restoring information.

Routines 1932 include communication routines 1936 and wireless terminal control routines 1938 . The wireless terminal control routine 1938 includes a transmitter control module 1940 , a receiver control module 1942 , and an error correction module 1946 . Data/information 1934 includes user data 1947, terminal identifier (ID) information 1948, received information 11950, received information N 1952, transmitted information 1 1954, transmitted information N 1956, identified MTU information 1958, partial information 1960, quality information 1962 and base station ID information 1964.

The user data 1947 includes data to be transmitted to and received from the base station 1800, as well as intermediate data such as data involved in a decoding process for recovering detected information. TransmitInfo1 1954 may include a set of information that may correspond to a first signal, e.g., a regular or basic signal, information defining the transport block that may be used to transmit the MTU of said first signal, defining the MTU that will be used to define said signal The information of the first set of MTUs on which the first set of MTUs will be modulated to define the information of the first signal defines which MTU information corresponding to the first signal information should be transmitted to eg a base station 1800 . In some embodiments, each MTU conveying the first set of informational data will be transmitted to base station 1800 . In other embodiments, most MTUs conveying the first set of information should be transmitted to base station 1800 . Transmission information N 1956 may include a set of information that may correspond to a second signal, e.g., a flashing signal, information defining a transport block that may be used, e.g. The information of the second set of MTUs of the second signal should be modulated on the second set of MTUs to define the information of the second signal. Received information 1 1950 includes a first set of information recovered from receiver 1 1902, such as information corresponding to the first set of base station pre-transmission information. The first set of recovered information may, for example, be recovered from conventional or base signals. Received information N 1952 includes a second set of information recovered from receiver N 1904, such as information corresponding to a second set of base station pre-transmission information. The second set of recovered information may, for example, be recovered from flashing signals.

The regular and flashing signals that define each original pre-emission group share some common MTU. The identified MTU information 1958 may include a set of MTUs identified in the second or flash signal, which may be obtained by the decoder 1920 of the receiver N. The identified MTU information 1958 can be forwarded to the receiver 1 1902, where the receiver 1902 can exclude those MTUs before passing the received signal to the error correction module in the decoder 1918, or alternatively, can forward the identified MTU information to Forwarded 1958 to error correction module 1946 in memory and/or error correction module in decoder 1918.

Terminal ID information 1948 is an ID assigned by a base station. Base station ID information 1964 includes information, such as a tilt value, that can be used to identify the particular base station to which wireless terminal 1900 is connected. Using the base station ID information 1964 and the terminal ID 1948, the wireless terminal can determine data and control the frequency hopping sequence. Quality information 1962 may include information from detected pilots, downlink channel quality measurements and reports, interference levels, power information such as current transmit level and battery level, SNR, and the like. In accordance with the present invention, quality information 1962 may be fed back to base station 1800 for use in classifying receivers as "stronger" or "weaker" receivers to facilitate scheduling and assignment by base station 1800, including assigning regular or Basic part and high speed part. Portion information 1960 may include the type of signal used for the portion, e.g. regular or basic versus flashing , to define the information for the section assigned to the user.

Communication routines 1936 include various communication applications that may be used to provide special services to one or more end node users, eg, IP telephony services, text services, and/or interactive games.

Wireless terminal control routines 1938 control the basic functions of wireless terminal 1900, including operation of transmitters 1910, 1912 and receivers 1902, 1904, signal generation and reception including data/control hopping sequences, status control, and power control. The wireless terminal control routine 1938 also controls and implements the new features and improvements of the present invention, including generating and transmitting composite signals, receiving composite signals, sorting composite signals into regular or base signal information and flashing signal information, sorting and restoring information.

In accordance with the present invention, transmitter control module 1940 may use data/information 1934 including transmit information 11954, transmit information N 1956, terminal ID 1948, user data 1947, and partial information 1960 to generate transmit signals and control transmitters 1910, 1912 operation. For example, transmitter control module 1940 may control transmitter 1910, via its encoder 1922, to encode the groups of information included in transmit message 1 1954 into a regular or base signal that transmitter 11910 may transmit. Transmitter control module 1940 may control transmitter N 1912, via its encoder 1924, to encode the groups of information included in message N 1956 into flashing or protected Signal. Alternatively, in various embodiments of the transmitters 1910, 1912, a single transmitter may be used that combines or mixes signals internally under the direction of the transmitter control module 1844 according to the transmit information 11954 and the transmit information N 1956. Such mixing operations may include superimposing regular and flash signals prior to transmission, and/or selectively forming an MTU transmission that includes each flash signal cell and the cells in the regular signal not included in the flash signal Group.

In accordance with the present invention, receiver control module 1942 controls the operation of receivers 1902, 1904 to receive the composite signal and extract two sets of information, such as receiver information 1 1950 and receiver information N 1952. Receive processing under the control of the receiver control module 1942 may include controlling the decoders 1918, 1920, as well as controlling other units within the receiver. In some embodiments, the receiver control module 1942 controls the impulse noise filtering, background noise filtering, and error detection modules together with the receivers 1902, 1904. In some embodiments, the receiver control module 1942 controls the second signal MTU identifier module in one receiver, e.g., receiver N 1904, and the discarding in another receiver, e.g., receiver 1 1902 module and pass the identified MTU information 1958 from receiver N 1904 to receiver 1 1902; this allows receiver 1 1902 to remove the MTU including the flashing signal information from the information stream entering the error correction module which attempts to recover the regular signal information group .

The error correction module 1946 operates in conjunction with or instead of an error correction module that may be included in the receiver 1902,1904. The error detection and correction capabilities included in receivers 1902, 1904 and/or module 1946 allow wireless terminal 1900 to reproduce a field corresponding to a pre-transmission field even if the (regular or underlying) signal representing the pre-transmission field has been corrupted. The superposition of the second flashing signal (flashing signal) or the breakdown phenomenon generated by the second signal (flashing signal), for example, the effect of replacing some MTUs.

On-off keying is a modulation technique in which the transmitter concentrates its energy along a subset of the degrees of freedom occupied by the codeword. For example, pulse position modulation is an example of on-off keying, where the transmitter uses energy only on those positions where a "1" is delivered, and cuts off when a "0" is delivered. By concentrating energy at one of M locations, pulse position modulation can deliver log2(M) bits. By using positive and negative pulses, additional bits can be transferred. An example of pulse position modulation is shown in Figure 3. FIG. 3 shows an illustration 300 of a typical individual slot 302 having 32 slots, for example. Energy is focused on the seventeenth slot 306 and represented by pulse 304 . In FIG. 3, if the pulse 304 can only be in one direction, such as the forward direction, then using 32 positions or slots, 5 bits of information can be conveyed. In FIG. 3, if the pulse 304 can be positive or negative, then using 32 positions or slots, 6 bits of information can be conveyed. In general, in the common case of on-off keying, information can be conveyed in two ways—first, the location of the energy within the degrees of freedom occupied by the codeword, and second, the signal contained in the occupied location information within. For example, if the mobile phone can estimate the channel by means of a reference signal, information can be encoded in the phase and/or amplitude in addition to the information encoded in the energy position of the general switching signal. In the remainder of this document, this common form of on-off keying will be referred to as flashing signaling. Typically, in the case of flash signaling, the concentration of energy is limited to a small subset of the available degrees of freedom.

According to the invention, flashing signaling can be used. What will be described is a simple example of flash coding according to the present invention. Consider an embodiment of the invention applied to a digital communication system using BPSK signaling. In the example considered here, it is assumed that the air link resource consists of 16 symbols. For example, in a typical spread spectrum OFDM multiple access system, the 16 air link resource symbols can be 16 orthogonal tones within one OFDM symbol period, or one tone within 16 OFDM symbol periods, Or any suitable combination of tone and symbol periods (eg, 4 tones within 4 OFDM symbol periods).

In FIG. 4, the superimposed signal 400 includes a conventional signal 420 conveyed using codewords with energy spanning all 16 BPSK symbols, as shown in FIG. 4 by the small unshaded rectangles. Conventional codewords can be constructed using, for example, convolutional codes. Assume that the protected signal is required to convey 5 information bits. In this embodiment, the five protected bits may be conveyed using the location of the high energy symbol 430 shown in FIG. 4 by the single shaded larger rectangle. The protected signal consists of a BPSK symbol 430 transmitted at high power, while superimposed on it is a regular signal 420 whose energy is distributed over 16 symbols. Note that the BPSK symbols of the protected signal can be located in any of 16 different symbol positions. For reference, a first symbol 401 and a sixteenth symbol 416 are identified in FIG. 4 . For example, in Figure 4, the BPSK symbol is transmitted on the 9th symbol. Thus, this symbol position conveys 4 of the 5 protected information bits. Furthermore, the phase (eg, sign) of the BPSK symbol conveys the 5th protected bit.

In order to see the advantages of the coding scheme of the present invention over the traditional overlapping coding scheme, the design of a stronger receiver is reconsidered. Stronger receivers can use the concept of sequential decoding. The stronger receiver first decodes the protected signal, then removes it from the received composite signal, and finally decodes the regular signal, or alternatively, signals the weaker signal receiver to discard the weaker signal detected on it. The tone of the large signal. Note that with the new encoding scheme of the present invention, even if the cancellation is not ideal, the damage to the conventional codeword is limited to one or a few symbols, so the receiver can minimize the adverse effects of this damage. For example, during decoding, a receiver can ignore symbols occupied by regular signals. In this case, the cancellation operation is simplified to cause cancellation at a specific symbol position, while it is possible to use an error correction code to correct the loss.

In the example of FIG. 4 above, each BPSK symbol of the 16 air link resource symbols represents one degree of freedom. A conventional signal distributes its energy across all 16 degrees of freedom. At the same time, each codeword of the protected signal concentrates its energy in one of the 16 degrees of freedom. Note that the blinking signal is an orthogonal code as defined in the above embodiments. However, the invention does not depend on any orthogonality properties of the codewords.

What will be described is a transmitter design for use in encoding implemented in accordance with the present invention. The foregoing examples illustrate the features and methods of the present invention, which can be implemented and utilized in a variety of communication systems. This method of superimposing signals by concentrating the energy of the protected signal among a small subset of the available degrees of freedom, while distributing the energy of the regular signal among substantially all of the available degrees of freedom, is referred to in this document as Flash overlay code. In this discussion, protected codewords are denoted as "flashing signals" and regular codewords are denoted as "regular signals" or "base signals". Although in general, the present method uses flashing signals to transmit protected information and regular signals to transmit regular information, in some embodiments of the invention this may be reversed.

According to the present invention, the flash signaling provides a method which allows a superimposed signal of superimposed coding gain to be well obtained in a practical receiver. In general, the same set of transmit resources is used to deliver flashing signals and regular signals. However, each codeword of the flashing signal concentrates its energy on a small subset of the available degrees of freedom. Each codeword of a regular signal can expand its energy in every available degree of freedom. In order to easily detect and decode a flicker signal, it is desirable that its energy be high, which in some embodiments is significantly higher than that of a conventional signal in a select subset corresponding to the degrees of freedom of the flicker signal. Even when the total energy of the regular signal is higher than that of the flashing signal, this relatively high energy concentration in the selected high-speed subset is feasible. Finally, for easy detection and decoding of regular signals, the impact of the flashing signal on the regular codeword should be minimal. In other words, the loss of energy in a selected subset of the degrees of freedom occupied by the flashing signal should have little effect on decoding regular codewords.

The choice of transmit power for flashing and regular signals is based on several factors, including (a) the SNR of the target receiver for both the high-speed and regular signals; (b) the information rate at which the high-speed and regular signals are conveyed; and (c) the high-speed and code constructors for regular signals. In general, powers can be chosen independently to meet their own robustness and coding performance requirements. Also, flash signaling can be performed in an opportunistic manner for maximum flexibility. In particular, a transmitter may opportunistically choose not to transmit flashing signals, and use most of its available power to transmit regular signals. Alternatively, the transmitter may choose to use the majority of its available power to opportunistically transmit flashing signals, and choose not to transmit regular signals.

A receiver design for use in encoding implemented in accordance with the present invention will now be discussed. In one embodiment of the invention, the receiver first decodes the flashing signal. This flicker signal is detectable at the receiver because it is received at a much higher power than a regular codeword in a small subset of degrees of freedom. The receiver then removes the effect of the flashing signal before attempting to decode the regular codeword. In the case of conventional superposition coding, cancellation consists of decoding the protected codeword and removing it from the received composite signal. In flicker superposition coding, in one embodiment, when a receiver would decode a regular signal, the receiver completely discards the signal received in a subset of the degrees of freedom of the decoded flicker signal codeword. Since a regular signal distributes its signal energy across all degrees of freedom, eliminating signal energy in a small subset of degrees of freedom will have little or negligible effect on decoding a regular codeword given the error detection and correction capabilities of the decoder performance impact.

In another embodiment of the invention, the receiver does not explicitly cancel the flashing signal before decoding the regular signal. Alternatively, the receiver decodes the regular signal directly from the received composite signal which may include the flashing signal. The receiver uses soft metrics plus saturation and inversion limits. Thus, the flicker signal serves to saturate or substantially eliminate signal components in the subset of degrees of freedom it occupies, but has a negligible impact on the performance of decoding regular codewords. Moreover, if the receiver is not interested in the flashing signal, the receiver can only decode the normal signal without decoding the flashing signal, in which case the receiver does not even need to be aware of the presence of the flashing signal, but can interpret it and / or considered pulse or background noise.

Embodiments of the control channel of the present invention are discussed below. In this section, an embodiment of the present invention applied to a control channel of a typical system will be described. In this example, in a cellular radio system 1700 as shown in FIG. 17, a control channel conveys information from a base station 1702 to a plurality of mobile users 1708, 1710 via a downlink broadcast channel. In most cellular radio systems, control channels are transmitted at broadcast power because they are bound by mobile users with the weakest channel. In this case, flashing signaling is well suited for the application and causes a significant power reduction with no or little loss of robustness.

It is assumed that the information carried on the control channel can be divided into subsets, each subset referring to one or more subsets of mobile users in the system. In this example, we assume that the control channel information can be divided into two subsets. The first subset is denoted "General Information" and is intended for those mobile users experiencing moderate to high downlink SNR. The second subset, denoted "protected information", is intended for a subset of users who experience a very low downlink SNR.

In the example considered here, it is assumed that the air link resource contains 32 symbols. For example, in a typical spread spectrum OFDM multiple access system, the air link resource could be 32 orthogonal tones within one OFDM symbol period, or one tone within 32 OFDM symbol periods, or any suitable Combinations of tones and symbol periods for (eg, 4 tones within 8 OFDM symbol periods).

As shown in the superimposed signal 500 of FIG. 5, a 32-symbol codeword is used to transmit conventional information 540, represented in this example by a small unshaded rectangle. For reference, a first symbol position 501 and a 32nd symbol position 532 are shown. The codewords are transmitted with sufficient power to be decoded by a subset of users experiencing a medium or higher SNR. Users with lower SNR may not be able to decode the codeword, so the power requirement is much lower than if the codeword had to be decoded by every mobile user. This difference in the ability to decode codewords is particularly true in wireless environments where mobile users can experience SNRs that vary by several orders of magnitude. Protected information intended for a subset of low SNR mobile users is transmitted using a flashing signal 550 as shown in FIG. 5, represented by 4 large shaded rectangles. In this embodiment, it is assumed that each protected codeword concentrates its energy on 4 symbol positions 502,512,520,530. Assuming in this example that the sets of 4 symbol positions are non-overlapping, this results in 8 orthogonal sets, each comprising 4 symbol positions. In general, however, in other configurations the groups of codewords may partially or completely overlap. Concentrating the energy of a protected codeword at more than one symbol position is important from the standpoint of providing diversity in a cellular radio system and provides a higher degree of protection against channel fading and interference.

In the example of Figure 5, each protected codeword subset conveys 3 bits only by its position. Let k be the index of 8 different groups of air link resource symbols. Assume that 32 air link resource symbols are indexed from 0-31. For k=0,...,7, the air link resource symbols at the kth symbol set position are symbols k, k+8, k+16 and k+24.

When the flash signal codeword includes multiple symbols, those symbols can be used to convey additional bits of information. Let {q0, q1, q2, q3} denote the four symbols to be transmitted using four air link resource symbols from any of the eight air link resource symbol groups. In one embodiment, {q0, q1, q2, q3} can be constructed using four Walsh codes of length 4 as listed in Table 1. The selection of q0, q1, q2 or q3 results in an additional 2 bits conveyed through the selection of 4 codewords.

Said information can be decoded at the mobile receiver in a simple manner. Due to the higher energy of the flash signal that is available to identify the location of the 3-bit symbol set, the mobile receiver can identify the location of the flash signal. It then extracts the symbol containing the flashing signal and decodes the remaining 2 bits. Examples of the described codeword structures result in codeword processing with non-uniform error protection properties. Bits resolved by the position of the flash signal are received with high reliability. This is particularly accurate when flashing signals are communicated over a wireless channel, since only one of the four symbol positions needs to be received to specify a codeword subset. The detection of q0, q1, q2 or q3 is more susceptible to bit errors from channel fading or interference. Alternatively, the receiver can employ a more complex decoder, such as a maximum likelihood decoder, to decode the full content of the flashing signal. Also, the invention is not dependent on the use of orthogonal codes on the flashing signal as shown in this example.

This concept can likewise be generalized to multivariate modulation groups in a simple manner. For example, if BPSK modulation is to be used, one more bit can be sent using the phase (ie, sign) of the flashing signal codeword. Also, if QPSK modulation is to be used, an extra bit can be sent using a choice of in-phase or quadrature signaling.

Table 1 Structure of Orthogonal Codes on Flashing Signals code word index Bit value of {q0, q1, q2, q3} 0 {+,+,+,+} 1 {+,+,-,-} 2 {+,-,+,-} 3 {+,-,-,+}

Flashing signaling in a multiple access channel according to the present invention will now be described. Although the invention has been described so far in the context of a broadcast channel, it is equally applicable in the structure of a multiple access channel. The described features of the invention will now be described in the context of the cellular uplink as a typical system of multiple access channels. Consider a base station receiver receiving signals from two mobile transmitters on the uplink. Since the base station 1702 is also the coordinating entity, it can distinguish the two transmitters by relative sensing. It is assumed that a mobile transmitter operating on a channel with a lower path loss is designated as a "stronger" transmitter, while another transmitter experiencing a higher path loss is considered a "weaker" transmitter. The base station instructs the weaker transmitter to transmit its signal by distributing the signal energy across each degree of freedom, while the stronger transmitter is instructed to concentrate its transmission energy over several degrees of freedom. The received composite signal 600 at the base station receiver 1802 is shown in FIG. 6 . The base receiver 1802 can easily decode and cancel the weak signal 620 transmitted from the "weaker" transmitter, represented by the large, shaded rectangle, before decoding the weak signal 620 transmitted from the "weaker" transmitter, represented by the small unshaded rectangle. "Flashing signal 610 from the transmitter.

The classification of mobile transmitters as "stronger" or "weaker" is not static, but rather defined relative to allow flexibility within the system. Instead of or in addition to the path loss experienced on the uplink channel, the notion of "stronger" or "weaker" mobile transmitters may be related to other criteria. The marking or classification of "stronger" or "weaker" mobile transmitters in some embodiments may be applied in the context of interference costs in the cellular uplink. For example, a mobile transmitter producing high uplink interference in other cells may be considered a "weaker" transmitter, and thus may be directed by the base station to transmit its signal by distributing energy across each degree of freedom. On the other hand, mobile transmitters that have low interference costs due to their location can be considered "stronger" transmitters and can use flash superposition coding to superimpose on the "weaker" transmitter's signal its signal. Alternatively, in some embodiments, mobile transmitters may be classified as "stronger" or "weaker" based on device constraints such as battery power or status.

What will be described is flashing signaling in a typical system according to the method and apparatus of the present invention. In a typical wireless data communication system, air link resources usually include bandwidth, time and power. Air link resources carrying data and/or voice traffic are called traffic channels. In a typical system, data is transferred through traffic channels in a traffic channel section (referred to simply as a traffic section). A traffic part can be used as the basic or smallest unit of available traffic channel resources. The downlink traffic portion carries data traffic from the base station to the wireless terminal, and the uplink traffic portion carries data traffic from the wireless terminal to the base station. In a typical system, the traffic segment consists of many frequency tones within a limited time interval.

In a typical system used to explain the invention, portions of traffic are dynamically shared between wireless terminals 1708, 1710 communicating with a base station 1702. A scheduling function, such as module 1838 in base station 1800, is arranged to allocate each uplink and downlink portion to one of the mobile terminals 1708, 1710 according to a number of criteria. Business parts can be assigned to different users from one part to another. For example, in FIG. 7 , in a graph 700 of frequency on the vertical axis 702 versus time on the horizontal axis 704, the base station scheduler assigns the portion A 706 shaded with a vertical line to User #1, which is shaded with a horizontal line. Portion B 708 of the representation is assigned to User #2. The base station scheduler can quickly allocate traffic channel parts to different users according to their traffic needs and channel status, which may generally change with time. In this way, traffic channels are efficiently shared and dynamically allocated among different users on a sector-by-sector basis. In a typical system, traffic channel portion allocation information is transmitted on an allocation channel comprising a series of allocation portions. In a cellular radio system such as the system 1700 shown in Figure 17, the allocation is typically transmitted in the downlink. There is an allocation section for the downlink traffic section, and a separate allocation section for the uplink traffic section. Each business part is associated with a unique assigned part. The associated allocation part conveys the allocation information of the business part. The assignment information may include identifiers of user terminals assigned to use said service part, and coding and modulation schemes used in said service part. FIG. 8 includes a graph 800 having a vertical axis 802 representing frequency and a horizontal axis 804 representing time. Figure 8 shows two distribution parts, distribution part A' (AS A') 806 and distribution part B' (AS B') 808, which convey the distribution information of service parts A (TS A) 810 and B (TS B) 812 . Assigned channels are shared channel resources. A user, such as a wireless terminal, receives the allocation information conveyed in the allocation channel and uses the traffic channel portion in accordance with the allocation information.

The data transmitted by the base station 1702 on the downlink traffic portion is decoded by the receiver in the intended wireless terminal 1708, 1710, while the uplink data transmitted by the assigned wireless terminal 1708, 1710 is decoded by the receiver in the base station 1702. Data transmitted on the road part. Typically, the transmitted portion includes redundant bits to assist the receiver in determining whether the data was decoded correctly. This is done because wireless channels can be unreliable, and useful data traffic usually has high integrity requirements.

The transmission of the service portion may succeed or fail due to interference, noise and/or channel fading in the wireless system. In a typical system, the receiver of a service part sends an acknowledgment to indicate whether the part was received correctly. Acknowledgment information corresponding to traffic channel portions is transmitted in an acknowledgment channel comprising a series of acknowledgment portions. Each business part is associated with a unique confirmation part. For the downlink traffic part, the acknowledgment part is in the uplink. For the uplink traffic part, the acknowledgment part is in the downlink. The acknowledgment part conveys at least one bit of information, for example, one bit, to indicate whether the relevant service part is received correctly. Due to the predetermined association between the uplink traffic part and the acknowledgment part, it may not be necessary to convey other information in the acknowledgment part, such as user identifier or part index. The acknowledgment portion is typically used by the user terminal, such as the wireless terminal 1708, 1710, using the relevant service portion, but not by other user terminals. Thus, in both links (uplink and downlink), the acknowledgment channel is a shared resource since it can be used by multiple users. However, there is usually no contention caused by using a shared acknowledgment channel, since there is usually no ambiguity in which user terminal will use a particular acknowledgment part. Figure 9 shows a graph 900 of downlink traffic segments, which includes a vertical axis 902 representing frequency, a horizontal axis 904 representing time, a first traffic segment, Service Part (TS) A 906, and a second traffic segment TS B 908. FIG. 9 also shows a second graph 950 of the uplink acknowledgment (ACK) portion, which includes a vertical axis 952 representing frequency and a horizontal axis 954 representing time. Figure 9 further shows two uplink acknowledgment sections, A"956 and B"958, which convey acknowledgment information for downlink traffic sections A906 and B908 from wireless terminal 1708 to base station 1702.

As noted above, exemplary system 1700 may be a packet-switched cellular wireless data system in which base station 1702 dynamically allocates portions of traffic on the downlink and uplink. Application of the present invention to exemplary system 1700 will now be described in the context of a cellular downlink. It is assumed that base station 1702 can allocate up to two traffic parts at a time in the form of time slots. The selection of which user the parts are intended for is broadcast on the allocation channel. It is further assumed without loss of generality that one of the two users is operating at a lower SNR than the other user. In this regard, two users are considered to be mutually "stronger" and "weaker".

The graph of FIG. 10 represents frequency on the vertical axis 1002 versus time on the horizontal axis 1004 . Figure 10 also includes an A (normal) allocation part (ASGr) 1006, an A traffic channel part (TCHa) 1008, an A (high speed) acknowledgment part (ACKf) 1010, a B high speed allocation part (ASGf) 1005, a B Traffic channel part (TCHb) 1007 and a B acknowledgment part (ACKr) 1009. ASGf 1005 is within the spectrum of ASGr 1006. ACKf 1010 is within the spectrum of ACKr 1009.

As shown in Figure 10, the allocation information for stronger users (ASGr) 1006 is transmitted on the allocation channel using regular signals, while the information for weaker users (ASGf) 1005 is conveyed using flashing signals. The stronger receiver knows from its (conventional) allocation that it will receive a service part denoted TCHa 1008, while similarly, through the flashing signal allocation (ASGf) 1005, the weaker receiver is informed denoted Its counterpart service part of TCHb 1007. In a typical system, mobile receivers 1708, 1710 provide a feedback acknowledgment to base station 1702 on the uplink to indicate the status of the received traffic portion.

As shown in FIG. 10, the two mobile users 1708, 1710 may superimpose their acknowledgment signals using the flashing signal. For this purpose, the "stronger" receiver on the downlink is assumed to be the stronger transmitter on the uplink, thus using the flash signal (ACKf) 1010 to convey its acknowledgment. The weaker receiver divides the energy of its acknowledgment signal in each degree of freedom and passes it on to the base station 1702 as a regular signal (ACKr) 1009 .

The capacity impact of cellular radio systems is now discussed for flash signaling. Cellular radio systems are generally interference bound, and their capacity depends on the amount of environmental interference and its characteristics. The use of flash signaling has a very significant impact on interference levels. Among all noise signals with the same energy, Gaussian noise yields the lowest capacity, which is a well-known information theory result. Flicker signals, due to their structure, are peaked and highly non-Gaussian in nature. Thus, given the same amount of interference, when one unit in a wireless system uses flashing signals, these signals have less impact (eg interference) on other units than if a signal like Gaussian is used. This applies to the uplink as well as downlink paths of cellular radio systems.

Figure 11 shows two exemplary groups of information that may be transmitted using one transport block, a first group of information 1150 and a second group of information 1160, in accordance with the present invention. The first information group 1150 includes information A ₁ 1151 , information A ₂ 1152 , and information A _N 1153 ; the second information group 1160 includes information B ₁ 1161 , information B ₂ 1162 , and information B _M 1163 . The first set of information can be, for example, user data, assignments or confirmations. The second information group can be, for example, user data, confirmation or allocation. 11 also shows a graph 1100 of minimum transmission units (MTUs), where the vertical axis represents frequency tones and the horizontal axis 1104 represents time. In FIG. 11 , each small box refers to a specific MTU unit, such as area 1112, and represents 1 degree of freedom that can be used to transmit information. Each slot on the horizontal axis, such as slot 1110, represents the time at which an MTU is transmitted, such as an OFDM symbol time. Each square in Figure 11, such as typical square 1114, represents an MTU unit. Each MTU corresponds to a unique resource combination for transmitting information, and the resource combination includes at least two of time, frequency, phase and spreading code. In OFDM systems, the MTU can be frequency or phase over time, eg, the in-phase or quadrature components in an OFDM tone-symbol. In a CDMA system, an MTU unit may be, for example, a spreading code assigned to a time unit. A typical transport block 1106 shown in FIG. 11 is a set of 24 MTUs. The information for the first information group 1150 is defined on the first set of minimum transmission units. The first set of minimum transmission units are identified by those squares with diagonals 1116 rising from left to right. A typical first set of MTUs includes 15 MTUs, for example, a typical MTU 1120 is in the first set of MTUs. In accordance with the present invention, the first set of MTUs includes at least a majority of the MTUs in the transport block 1106 . In some embodiments, the first set of MTUs includes at least 75% of the MTUs in the transport block 1106 . The example of FIG. 11 is an embodiment that includes 15 MTUs of the first set/20 total MTUs of blocks 1106 = 75%. Information for the second set of information 1160 is defined on the second set of minimum transmission units. The second set of minimum transmission units are identified by those squares with diagonals 1118 descending from left to right. A typical second set of minimum transmission units includes 3 MTUs. According to the invention, the second set of MTUs comprises fewer MTUs than the first set of MTUs, and some of the MTUs in the first and second set of MTUs are the same. For example, in FIG. 11, 2 MTUs, MTU 1122 and MTU 1123, are included in two groups. In some embodiments, the second set of MTUs is less than half the number of MTUs of the first set of MTUs; FIG. 11 is an example of such an embodiment. The information in the first and second information sets 1150, 1160 may be communicated, for example, from the base station 1702 to the wireless terminal 1708, 1710 using the minimum transmission units comprised in the first and second sets of minimum transmission units.

FIG. 12 shows a graph 1200 of minimum transmission unit (MTU) on the vertical axis 1202 versus time on the horizontal axis 1204 . Figure 12 shows a typical transport block 1205 comprising an MTU of 1600. The first set of information may be represented by a first set of MTUs comprising a majority of the 1600 MTUs in transport block 1205 . In accordance with the present invention, transport block 1205 may be subdivided into sub-blocks. In FIG. 12, the MTU transport block 1205 is divided into sub-blocks of 16 MTUs, each sub-set comprising 100 MTUs. Each small square, such as typical square 1206, includes a sub-block of one MTU. In some embodiments, the first set of MTUs may be subdivided into small groups of information, each group represented by the first set of MTUs within a separate sub-block. In combination, the small set of information represents the first set of information encoded over a large portion of the large transport block 1205 . A typical sub-block 1207 represents 100 typical MTUs of a typical sub-block. Typical sub-block 1208 represents 100 typical MTUs of another sub-block. The individual MTUs of the other sub-blocks of transport block 1205 are not drawn, but each other sub-block can be assumed to be similar to typical sub-block 1207 . Each circle in a sub-block represents an MTU. Each diagonal line rising from left to right through a circle represents a separate MTU for representing information in the first information group. Each diagonal line descending from left to right through a circle represents a separate MTU for representing information in the second information group. In FIG. 12, typical MTU 1208 is one of the MTUs used to represent the first information group; typical MTU 1211 is another MTU used to represent the first information group. In certain cases, the typical MTU 1209 is not used to represent information in the first or second information group, although it is within the scope of the typical transport block 1205. That is, at the particular point in time shown, MTU 1209 is not used to communicate signals corresponding to either the first or second information groups. A typical MTU 1210 is used to represent information in both the first information group and the second information group.

In the example of FIG. 12, each sub-block, such as sub-block 1207, may be used to represent information that uniquely represents a portion of the first set of information that is uniquely defined on a small sub-block of the MTU. However, the second set of information may represent a different set of information, for example 10 bits of information. In order to uniquely transmit 10 bits of information, 2 ¹⁰ =1024 possible minimum transmission units may be required. A transport block 1205 with 1600 available smallest possible transport units may be used, and a single MTU is assigned a specific value to represent 10 bits of information. In this example, when transmitting information, MTU 1210 is the only MTU used to convey the information of the second information group. FIG. 12 shows the case where each MTU included in the second set of MTUs is also included in the first set of MTUs.

Figure 131301 shows a method for transmitting two packets, eg, packets 1150 and 1160 of Figure 11, in accordance with the present invention. 13 includes a first device, such as device 1 1302 containing a transmitter, transmitter 1 1304, and a second device, such as device 2 1308, containing a transmitter, transmitter 2 1310. Each device may be, for example, a base station or a wireless terminal of the type shown in FIG. 17 . The first set of information 1150 is communicated by a signal transmitted from transmitter 1 1304, such as signal 1 1306. Signal 1 1306 is sometimes called the base or regular signal. The second set of information 1160 is conveyed by a signal transmitted from transmitter 2 1310, such as signal 2 1312. Signal 2 is sometimes called a flashing signal. In the typical case of Figure 13, signal 1 1306 will use the first set of minimum transmission units, while signal 2 1312 will use the second set of minimum transmission units. Some of the first set of MTUs transmitted by transmitter 1 1304 will be the same as some of the second set of MTUs, causing some superposition of signal 1 1306 and signal 2 1312.

FIG. 14 shows two methods for transmitting two packets, eg, packets 1150 and 1160 of FIG. 11, in accordance with the present invention. In the first method described in FIG. 14, a typical device 3 1402, such as a base station or a wireless terminal, includes a transmitter capable of transmitting signals corresponding simultaneously to the first and second information groups 1150, 1160, respectively, That is transmitter 31404. In FIG. 14, signal 3 1406 corresponds to first packet 1150 and uses a first set of MTUs, while signal 4 1408 corresponds to second packet 1160 and uses a second set of MTUs. Signal 3 1406 is sometimes called the base signal or regular signal, while signal 4 1408 is sometimes called the flashing signal. Signal 4 1408 is transmitted at a higher power level than Signal 3 1406 on a per minimum transmission unit basis. In some embodiments, signal 4 1408 is transmitted at a power level that is at least 3 dB greater than the power level at which the smallest transmission unit corresponding to signal 3 1406 is transmitted. In some embodiments, the transmit power level of the smallest transmission unit used to transmit Signal 3 1406 may be varied. The transmit power level of the MTU used to transmit the signal 4 1408 may also be changed.

In the second method described in FIG. 14, a typical device, Device 4 1410, such as a base station or wireless terminal, includes a transmitter, Transmitter 4 1412. Transmitter 4 1412 includes a first signal module 1411 and a second signal module 1413. The first signal module 1411 generates a signal 5 1414 corresponding to the first packet 1150. The second signal module 1413 generates a signal 6 1416 corresponding to the second packet 1160. Signal 5 1414 and Signal 6 1416 are combined by combiner module 1418 prior to transmitting the MTU in signal 1420. Signal 5 1414 is sometimes called the base or regular signal, while signal 6 1416 is sometimes called the flashing signal. The combiner module 1418 may perform the superposition of two signals, Signal 5 1414 and Signal 6 1416. Alternatively, combiner module 1418 may compare the set of MTUs to be used for transmit signal 5 1414 with the set of MTUs to be used for transmit signal 6 1416. The combiner module 1418 may direct the information in signal 6 1416 into each requested MTU; however, the module 1418 may exclude those MTUs that have been allocated to convey signal 6 1416 from the set of MTUs allocated to signal 5 1414. For example, in the example of FIG. 11 , MTU 1122 and MTU 1123 can be made to refuse to transmit the information of signal 5 1414. In this way, the second packet 1160 in signal 6 1416 breaks through or replaces the first packet 1150 in signal 5 1414 (which would occupy the same MTU). This embodiment assumes that the receiver has sufficient error detection and correction capabilities to recover the original first packet 1150 for which some information was not transmitted. In this way, instead of using the actual superposition, the signals corresponding to the second group can be transmitted to discard overlapping signals of the first group without superimposing them on the signals of the first group before the actual transmission. In this case, the MTU breakdown used to convey the second set of information is selected in the common transport block to transmit the set of MTUs of the first set of information.

Figure 15 shows a typical device, device 5 1502, such as a base station or wireless terminal, which can be used to receive a composite signal and obtain two sets of received information, information A' 1516 and information B' 1518, in accordance with the present invention. Information A' 1516 is a recovered set of information corresponding to the first set of original pre-transmission information (ie, Information A 1150 of FIG. 11). Information B' 1518 is a recovered information set corresponding to the first set of original pre-transmission information (ie, Information B 1160 of FIG. 11). Device 5 1502 includes a first receiver, receiver 1 1506, that includes an impulse noise filter 1510 and an error correction module 1512. Contains signals transmitted together over time, for example, a composite signal of signal 3 1406 of FIG. 13 (regular or fundamental signal) and signal 4 1408 of FIG. 13 (flashing signal), i.e. signal 8 1520, received by receiver 1 1506 , wherein the impulse noise filter 1510 filters or rejects signals corresponding to MTU units originating from the second field 1160 . The remaining signal corresponding to most of the MTUs in the MTU group corresponding to the first packet 1150 (regular signal) is processed by the error correction module 1512, which recovers the "lost information", so that the received packet A' 1516 is A good reproduction of the pre-transmission packet A 1150. Device 5 1502 also includes a second receiver, receiver 2 1508, that includes a background noise filter 1514. The composite signal 8 1520 also enters receiver 2 1508, where background noise filtering 1514 treats the signal corresponding to the first packet 1150, e.g., signal 3 1406, as noise and removes or rejects this low level signal, leaving the signal ( For example flashing signal), the good reproduction of the second information group B 1160 that transmits in advance can be reproduced as received information group B' 1518 thus.

Similar to device 5 1502, a second device, device 6, as shown in Figure 15, performs composite signal reception and information recovery. Device 6 1532 includes a first receiver, receiver 1 1536, and a second receiver, receiver 2 1538. Receiver 1 1536 includes a decoder, decoder 1 1540, which includes a pulse filter 1544 and error correction module 1546. Receiver 2 1538 includes a decoder, decoder 2 1542, including a background noise filter 1548. The operation of Device 6 1532 is similar to that described for Device 5 1502, except that additional decoding is done in Device 6 1532. During operation, receivers 1536 and 1538 operate independently and in parallel. The first receiver 1536 treats the flicker signal as impulsive noise and rejects the high speed symbols as impulsive noise, or performs other operations such as saturating the high speed components as any other impulsive noise signal might be processed. Receiver 2 1538 decodes the flashing signal while viewing the lower power signal as background noise. Composite signal 9 1554 is similar to composite signal 8 1520 which includes both regular and flashing signals. Received field A" 1550 corresponds to a good rendition of the original first pre-transmission field A 1150 of FIG. 11. Received field B" 1552 corresponds to a good reproduction of the original second pre-transmission field B 1160 of FIG. reproduction.

FIG. 16 shows another typical device, device 7 1562, such as a base station or wireless terminal, which includes a first receiver, receiver 1 1563, and a second receiver, receiver 2 1564. Receiver 1 1563 includes a decoder 1565 including a discarding module 1570 and an error correction module 1566. Receiver 2 1564 includes a decoder 1566 including a background noise filter 1567 and a second signal MTU identifier module 1568. The composite signal 10 1573 is received and enters receiver 2 1564. In decoder 1566 of receiver 2 1564, the signal may be filtered by background filtering 1567 and the information decoded and output as field B' 1572, a reproduction of the original pre-transmission field B 1160 of FIG. 11 . In addition, the second signal MTU identifier module 1568 identifies a set of MTUs 1569 corresponding to the second (flashing) signal and sends said information 1573 to the decoder 1565 of the receiver 1 1563. In some embodiments, the identified MTU group 1573 is one of the in-phase and quadrature components of the tone at different symbol times.

The discard module 1570 of the decoder 1565 in the receiver 1 1563 receives the identified MTU groups 1573 and rejects or removes information originating from those MTU units before the information enters the error correction module 1566. Alternatively, the information identifying the MTU of the second or "flashing" signal may be passed directly to the error correction module 1566, which may remove the influence from those MTUs. Field A'1571 corresponds to a reproduction of the first pre-transmission field 1150 of FIG. Discarding identified MTUs and their effect on lower power signals is in stark contrast to prior art superposition decoding techniques that require precise removal of high power signal components from received signal units before the underlying signal can be recovered.

Although described in the context of an OFDM system, the methods and apparatus of the present invention are applicable to a wide variety of communication systems, including many non-OFDM and/or non-cellular systems.

In various embodiments, the nodes described herein are implemented using one or more modules to perform steps corresponding to one or more methods of the invention, such as signal processing, message generation and/or transmission steps. Thus, in some embodiments, various features of the invention are implemented using modules. Such modules may be implemented using software, hardware, or a combination of software and hardware. Many of the methods or method steps described above may be implemented using machine-executable instructions, e.g., software contained within a machine-readable medium, e.g., a storage device such as RAM, floppy disk, etc., to control a machine, e.g., with or without additional A general-purpose computer of hardware to implement all or part of the methods described above, for example in one or more nodes. Therefore, it should be noted that the present invention is directed to a machine-readable medium comprising machine-executable instructions to cause a machine, such as a processor and related hardware, to perform one or more steps of the methods described above.

Many additional variations on the methods and apparatus of the invention described above will be apparent to those skilled in the art in view of the above description of the invention. Such variations are to be considered within the scope of the present invention. The methods and apparatus of the present invention may, and in various embodiments are, be used in conjunction with CDMA, Orthogonal Frequency Division Multiplexing (OFDM), and/or various other types of wireless communication between an access node and a wireless terminal. The communication technology used together with the communication link. In some embodiments, a base station establishes a communication link with a mobile node using OFDM and/or CDMA. In various embodiments, a wireless terminal is implemented as a notebook computer, personal digital assistant (PDA), or other portable device including receiver/transmitter circuitry and logic and/or routines to implement the methods of the present invention.

The techniques of the present invention may be implemented using software, hardware, and/or a combination of software and hardware. The invention is directed to devices such as wireless terminals, base stations, communication systems implementing the invention. It is also directed to methods, eg, methods of controlling and/or operating wireless terminals, base stations and/or communication systems, such as hosts, in accordance with the present invention. The invention is also directed to a machine-readable medium, such as ROM, RAM, CD, hard disk, etc., comprising machine-readable instructions for controlling a machine to implement one or more steps in accordance with the invention.

Claims (23)

1. A method of transmitting at least a first and a second set of information using a transport block, said transport block comprising a plurality of minimum transmission units, each minimum transmission unit corresponding to a unique combination of resources for transmitting information, The resource includes at least two of time, frequency, phase and spreading code, and the method includes: defining a first set of said smallest transmission units for conveying said first set of information, said first set comprising at least a majority of said transport block; defining a second set of said minimum transmission units for conveying said second set of information, said second set of minimum transmission units comprising fewer minimum transmission units than the first set; the first and second sets of minimum at least some of the smallest transmission units in the transmission units are the same; and The first and second sets of information are transmitted using minimum transmission units contained in said first and second sets of minimum transmission units. 2. The method of claim 1, wherein said information is at least one of user data and control information including acknowledgment and assignment information. 3. The method of claim 1, wherein communicating the first and second sets of information comprises separately transmitting signals corresponding to the first and second sets of information from different transmitters. 4. The method of claim 3, wherein said different transmitters are placed on different devices. 5. The method of claim 1, wherein signals corresponding to said first and second sets of information are transmitted from the same transmitter. 6. The method of claim 1, wherein said first set of minimum transmission units comprises at least 75% of the total number of minimum transmission units in said transport block. 7. The method of claim 6, wherein said second set of minimum transmission units is less than half the number of minimum transmission units of said first set of minimum transmission units. 8. The method of claim 6, wherein each minimum transmission unit contained in the second set of minimum transmission units is also contained in said first set of minimum transmission units. 9. The method of claim 1, wherein communicating the first and second sets of information includes transmitting the second set of information using each of the smallest transmission units of the second set of smallest transmission units, and Wherein communicating the first set of information includes transmitting said first set of information, including transmitting at least some of said first set of minimum transmission units. 10. The method of claim 9, wherein said at least some first set of minimum transmission units includes only minimum transmission units that are not included in said second set of minimum transmission units. 11. The method of claim 9, wherein said at least some of said first set of minimum transmission units comprise minimum transmission units in said second set. 12. The method of claim 11 , wherein at least the first and second signals are used to convey the first and second sets of information, respectively, and wherein the method further comprises combining the first and second signals for use in the The composite signal is formed before the minimum transmission units of the first and second sets of minimum transmission units transmit the composite signal. 13. The method of claim 1, wherein the second signal is transmitted at a higher power level than said first signal on a per minimum transmission unit basis; and The first and second sets of information passed include: using minimum transmission units includes using at least some of the minimum transmission units contained in said first set of minimum transmission units to transmit a first signal corresponding to a first set of information; and A second signal corresponding to the second set of information is transmitted using a minimum transmission unit in the second set of minimum transmission units. 14. The method of claim 13, wherein the power level at which the minimum transmission unit corresponding to the second signal is transmitted is at least 3 dB greater than the power level at which the minimum transmission unit corresponding to the first signal is transmitted. 15. The method of claim 13, further comprising changing a transmission power level of the smallest transmission unit used to transmit the second signal. 16. The method of claim 13, further comprising varying a transmission power level of a smallest transmission unit used to transmit said first signal. 17. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, said first and second signals sharing an overlapping set of communication resources, wherein said overlapping resources include time, frequency , at least two of phase and spreading codes, said means comprising: a first receiver for receiving said composite signal from a communication channel, said first receiver including a filter for treating a portion of said composite signal corresponding to said second signal as impulse noise ;as well as a second receiver arranged in parallel with said first receiver for receiving said composite signal from said communication channel, said second receiver comprising a device for converting said composite signal corresponding to said The portion of the first signal is treated as background noise by the filter. 18. An apparatus according to claim 17, wherein said apparatus includes error correction means for recovering information lost by treating portions of said composite signal corresponding to said second signal as impulsive noise. 19. The method of claim 17, wherein said first and second signals share the same frequency band. 20. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, the apparatus comprising: A first receiver for receiving a composite signal, said first receiver comprising: i) a first filter module for filtering impulse noise from said received composite signal, a portion of said signal corresponding to a second signal being considered as impulse noise by said filter module; and ii) a first decoder connected to said first filter module for decoding information corresponding to a first signal, said first decoder determining a composite signal value received over a first set of minimum transmission units; as well as a second receiver comprising: i) a second filter module for filtering background noise from said received composite signal; and ii) a second decoder connected to said second filter module for decoding information corresponding to a second signal, said second decoder determining a composite signal value received on a second set of minimum transmission units, A majority of the second set of smallest transmission units is included in the first set of transmission units. 21. An apparatus for receiving a composite signal comprising first and second signals transmitted together over time, said apparatus comprising: a second receiver for receiving a composite signal and identifying a minimum transmission unit in said composite signal corresponding to said second signal, said second receiver outputting information identifying said identified minimum transmission unit corresponding to said second signal The minimum transmission unit of two signals; and a first receiver for receiving said composite signal, said first receiver comprising a decoder for decoding a portion of said composite signal corresponding to said first signal, said decoder receiving said information to identify the identified minimum transmission unit corresponding to the second signal, and discard the identified minimum transmission unit corresponding to the second signal. 22. The apparatus of claim 21, wherein said identified elements corresponding to the second signal are one of in-phase and quadrature components of tones at different symbol transmission times. 23. The apparatus of claim 21, wherein said first receiver comprises: An error correction circuit for recovering information of the first signal lost due to discarding of said identified transmission unit corresponding to the second signal.

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