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WO2007113730A1 - Station mobile pour un reseau de communication base sur plusieurs canaux - Google Patents

Station mobile pour un reseau de communication base sur plusieurs canaux Download PDF

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Publication number
WO2007113730A1
WO2007113730A1 PCT/IB2007/051061 IB2007051061W WO2007113730A1 WO 2007113730 A1 WO2007113730 A1 WO 2007113730A1 IB 2007051061 W IB2007051061 W IB 2007051061W WO 2007113730 A1 WO2007113730 A1 WO 2007113730A1
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WIPO (PCT)
Prior art keywords
mobile station
information
channel
transmission
sending
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Ceased
Application number
PCT/IB2007/051061
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English (en)
Inventor
Hans-Juergen Reumerman
Georgios Orfanos
Bernard Walke
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Intellectual Property and Standards GmbH
Koninklijke Philips Electronics NV
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Publication of WO2007113730A1 publication Critical patent/WO2007113730A1/fr
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user

Definitions

  • the present invention relates to a mobile station for a multi-channel based communications network and to a method for transmitting information over such a network. More particularly, the present invention relates to a mobile station for a multi-carrier code division multiple access wireless local area network and to a method for transmission of information over such a network. Further, the communications network may also be a IEEE 802.1 la,e based communications network extended for operation in multiple channels.
  • US 2004/0264475 Al describes an architecture for multi-channel carrier-sense multiple access systems using an 802.11 protocol.
  • the architecture known from US 2004/0264475 Al comprises: in a MAC for a station, plural transmit queues, a queue selection mechanism, and a holding queue; a physical layer having multiple channels therein; and in a receiver for a station, a re-ordering buffer for ordering packets in a proper sequence prior to the packets leaving the receiver.
  • the 802.11 wireless local area network protocol uses carrier sense multiple access/collision avoidance for its access mechanism.
  • a feature of this mechanism is that it senses the channel selected by the transmitting station prior to transmission, and if the channel is found to be busy, the station defers transmission for a pseudo-randomly chosen period of time.
  • collisions are avoided by having each station maintain a network allocation vector based on the duration values of frames to be transmitted, thereby providing an increase in throughput over what might be achieved in a given single channel system.
  • the present invention has the further advantage that it allows an efficient sharing of system resources among the mobile stations and prioritizes the forwarding mobile station. Additionally, a forwarding mobile station can transmit more than one packet in parallel, which increases overall performance of a multihop connection and reduces the delay.
  • the measure as defined in claim 2 has the advantage that the duration of the guard interval in which the mobile station is pausing, is optimized with respect to a necessary duration for data transmission determined by a transmission window duration.
  • a transmission window duration may be a part of the information, i.e. the data packet to be transmitted, or may be determined by a measurement of the duration that was necessary to transmit a certain data packet transmitted.
  • the measure as defined in claim 3 has the advantage that further information may be sent from the mobile station to a succeeding mobile station without interfering with the first information forwarded by further mobile stations over a channel used for forwarding the first information.
  • the measure as defined in claim 4 has the advantage that a direct acknowledgement, for example a acknowledgement or a negative acknowledgement, can be omitted to reduce the traffic over the network.
  • a direct acknowledgement for example a acknowledgement or a negative acknowledgement
  • the preceding mobile station Due to the use of the upper transmission power for sending at least a part of the first information, the preceding mobile station is enabled to successfully receive a part of the first information already sent from the preceding mobile station to the mobile station. Hence, the preceding mobile station is enabled to determine that the mobile station continues transmission of the first information, and therefore the preceding mobile station is enabled to determine that the first information has been successfully transmitted to the mobile station. Hence, reception of the first information by the preceding mobile station is a reliable indirect acknowledgement.
  • the measures as defined in claims 5 and 6 have the advantage that, for example from an unique identification number stored in the header information of the first information, the preceding mobile station determines whether the first information has been successfully transmitted or not at an early time instant so that it must listen only to a part of the first information sent from the mobile station. Further, the other part of the first information may be sent with a lower transmission power than the upper transmission power to reduce a channel interference.
  • the measure as defined in claim 7 has the advantage that the mobile station is not transmitting to an already busy mobile station so that collisions are reduced. Thereby, the not available timer may be a network allocation vector.
  • the measure as defined in claim 8 has the advantage that collisions in multihop scenarios are reduced, while smart back-off deployment is enabled.
  • Fig. 1 shows a mobile station according to a preferred embodiment of the present invention
  • Fig. 2 illustrates a data transmission method according to a first embodiment of the present invention
  • Fig. 3 illustrates the utilization of channels by the method according to the first embodiment of the present invention
  • Fig. 4 illustrates a data transmission method according to a second embodiment of the present invention
  • Fig. 4A illustrates an information sent by a data transmission method according to the second embodiment of the present invention
  • Fig. 5 illustrates a spreading method according to an embodiment of the present invention
  • Fig. 6 illustrates an utilization of channels by a method according to an embodiment of the present invention
  • Fig. 7 illustrates an utilization of channels by a method comprising smart back-off according to an embodiment of the present invention
  • Fig. 8 shows a star scenario arrangement of mobile stations to illustrate an embodiment of the present invention
  • Fig. 9 shows a diagram showing a simulated scenario for multihop transmissions
  • Fig. 10 shows a diagram showing a carried end-to-end traffic per multihop connection vs. offered load
  • Fig. 11 shows a diagram showing a mean end-to-end queuing delay per multihop connection vs. offered load
  • Fig. 12 shows a diagram showing a mean end-to-end service time per multihop connection vs. offered load
  • Fig. 13 shows a diagram showing a cumulative distribution function (CDF) of queuing delay per hop for 0.75 Mbit/sec offered load per connection;
  • CDF cumulative distribution function
  • Fig. 14 shows a diagram showing a CDF of queuing delay per hop for 1.25 Mbit/sec offered load per connection;
  • Fig. 15 shows a diagram showing a CDF of end-to-end delay per multihop for 0.75 Mbit/sec offered load per connection.
  • Fig. 16 shows a diagram showing a CDF of end-to-end delay per multihop connection for 1.25 Mbit/sec offered load per connection.
  • Fig. 1 shows a schematic structure of a mobile station 1 according to a preferred embodiment of the invention.
  • the mobile station 1 can be used in multi-carrier code division multiple access wireless local area networks.
  • the mobile station 1 and the method described below are applicable but not limited to a multihop medium access control protocol on the basis of IEEE 802.1 la,e.
  • the mobile station 1 and the method for such a mobile station are, generally, applicable for wireless communication systems with a multichannel structure.
  • the mobile station 1 comprises a receiving and sending unit 2 connected with an antenna 3. Further, the mobile station 1 comprises a control unit 4 for controlling the receiving and sending unit 2. Thereby, the receiving and sending unit 2 and the control unit 4 are connected over a connection 5.
  • the mobile station 1 comprises a timer unit 6 that is connected via a connection 7 with the control unit 4.
  • the timer unit 6 comprises one or more not available timers, wherein the control unit 4 can set one of the available timers to a not available time interval for a channel CCHl , CCH2 (Fig. 3).
  • Fig. 2 illustrates a method according to the first embodiment of the present invention
  • Fig. 3 illustrates a utilization of channels CCHl, CCH2 by such a method.
  • the method and the utilization of channels CCHl, CCH2 is illustrated with reference to mobile stations MSl, MS2, MS3, MS4, each of which is arranged according to the mobile station 1, as shown in Fig. 1.
  • a ready-to-send (RTS) packet is sent from mobile station MSl.
  • This ready-to-send packet is received from mobile station MS2 between timing tl to timing t2.
  • the mobile station MS2 answers the ready-to-send packet with a transmission of a corresponding clear-to-send (CTS) packet sent during the time interval from timing t3 to timing t4.
  • CTS clear-to-send
  • the clear-to-send packet sent from mobile station MS2 is received by mobile station MS 1 , and after a short interframe space interval from timing t4 to timing t5, the mobile station MSl begins data transmission of data Dl from timing t5 to timing t6. This data Dl is received by the mobile station MS2. After reception of the data Dl sent from mobile station MSl and a short interframe space interval from timing t6 to timing t7, the mobile station MS2 sends an acknowledgement between timing t7 and timing t8 to the mobile station MS 1 , when the data Dl has been successfully received.
  • the control unit 4 of the mobile station MSl determines a successful transmission of the data Dl and controls the receiving and sending unit 2 of the mobile station MS 1 so that a transmission to the mobile station MS2 is halted during a guard interval 8.
  • the receiving and sending unit 2 of the mobile station MSl is controlled so as to pause transmission to the succeeding mobile station MS2 during the guard interval 8.
  • the guard interval 8 begins at timing t8 and ends at timing tl6.
  • the mobile station 2 forwards the information comprising the data Dl over the channel CCHl to a further mobile station MS3, as described in the following.
  • the mobile station MS2 After a back-off BO beginning at timing t8, the mobile station MS2 sends a ready-to-send packet to the mobile station MS3 over the channel CCHl from timing t9 to timing tlO. After a short interframe space interval from timing tlO to timing tl 1, the mobile station MS3 answers the ready-to-send packet from mobile station MS2 with a clear-to-send packet, wherein the clear-to-send packet is sent from timing tl 1 to timing tl2. The mobile station 2 receives the clear-to-send packet and, after a short interframe space interval from timing tl2 to timing tl3, the data Dl is forwarded to the mobile station MS3 during the time interval from timing tl3 to timing tl4.
  • the mobile station MS3 receives the data Dl and, after a short interframe space interval from timing tl4 to timing tl5, answers with an acknowledgement between timing tl5 and timing tl6, because the data Dl has been successfully received.
  • the guard interval 8 of mobile station 1 expires so that the receiving and sending unit 2 of the mobile station 1 continues with transmission of further information to the mobile station MS2.
  • the mobile station MSl may transmit the further information to mobile station MS2 over another channel, for example channel CCH2, to avoid collision with data sent from mobile station MS3 when the mobile station MS3 is connected with mobile station MS4 over channel CCHl.
  • data Dl is transmitted from mobile station MS3 to mobile station MS4 parallel to the transmission of data D2 from mobile station MSl to mobile station MS2, wherein different channels CCHl, CCH2 are used to increase overall performance of the multihop connection and to reduce a possible delay in information transmission.
  • channel CCH2 is not used by any one of mobile stations MSl, MS2 or MS3 during the time interval from timing t2 to timing tl6, but may be used by other mobile stations, for example mobile station MS4, for data transmission.
  • a not available timer is set for channel CCHl in the timer unit 6 of mobile station MS3, because channel CCHl is used by the adjacent mobile station MS2 and the neighboring mobile station MSl.
  • the not available timer set in the timer unit 6 of the mobile station MS3 from timing t2 to timing t8 is not only set to the channel CCHl, but also with respect to the mobile stations MSl and MS2.
  • the control unit 4 of the mobile station MS3 determines the other mobile stations MSl and MS2 using the channel CCHl from this information set in the timer unit 6, and controls the receiving and sending unit 2 of the mobile station MS3 so as to pause transmission to mobile station MS2 over the free channel CCH2 during the not available time interval from timing t3 to timing t8. This applies also to a succeeding mobile station, for example to the mobile station MS4 succeeding mobile station MS3.
  • Fig. 4 illustrates a data transmission method according to a second embodiment of the present invention. From timing tl to timing t6 information is transmitted from the mobile station MSl to the mobile station MS2, as described in detail with reference to Fig. 2 and 3. But, at timing t20 that corresponds to timing t7 in Figs. 2 and 3, the mobile station MS2 continues directly with transmission of data Dl. Thereby, as shown in Fig. 4A, a part 10 of the data Dl comprising a header information 11 is sent with an upper transmission power, and another part 12 of the data Dl is sent with a normal transmission power.
  • the control unit 4 of the mobile station MS2 determines the upper transmission power for sending the part 10 of the data Dl as a maximum of a transmission power required to transmit information to the mobile station MS 1 and a transmission power required to transmit information to the mobile station MS3.
  • the receiving and sending unit 2 of the mobile station MS2 can successfully send the part 10 of the data Dl both to the mobile station MSl and the mobile station MS3.
  • the mobile station MSl identifies the data Dl between timing t20 and t21 as the data Dl already send between timing t5 and t6 from the header information 11.
  • the control unit 4 of the mobile station MSl determines reception of the part 10 of the data Dl comprising the header information 11 as an indirect acknowledgement for a successful transmission of data Dl to the mobile station MS2.
  • the other part 12 of the data Dl may be transmitted with a normal transmission power, wherein the normal transmission power is determined as the transmission power necessary to transmit information from the mobile station MS2 to the mobile station MS3.
  • the receiving and sending unit 2 of the mobile station 1 may stop reception of the data Dl after reception of the header information 11 at timing t24, wherein the timing t24 is between the timing t20 and the timing t21.
  • the mobile station MS3 may answer the received data Dl with a clear-to-send packet after a short interframe space interval between timing t21 and timing t22. The transmission of the clear-to-send packet is then between timing t22 and timing t23.
  • the clear-to-send packet between timing t22 and timing t23 may be sent after reception of the part 10 of the data Dl so that the other part 12 of the data Dl is transmitted from the mobile station MS2 to the mobile station MS3 after reception of the clear-to-send packet.
  • utilization of the communications network may be further optimized in case of a huge or large amount of data Dl.
  • the header information 11 may be the serial number or a unique identification number of the data packets to be transmitted or acknowledged. Further, it should be noted that delaying the reception of a packet in a channel CCHl, CCH2 for a certain time, for example the short interframe space interval SIFS, enables parallel reception in two channels CCHl and CCH2. This applies for mobile stations 1 equipped with more than one receiver.
  • multihop transmissions are essential for coverage extension and interconnection of different subnetworks.
  • WLAN Wireless Local Area Networks
  • One of the ways to provide continuous coverage is deploying multihop networks.
  • a multihop functionality extension for the Multi- Carrier Code Division Multiple Access (MC-CDMA) based Distributed Coordination Function (DCF) is presented.
  • the described Medium Access Control (MAC) protocol deals efficiently with the problem of packet forwarding without raising the system's complexity, while exploiting the multi channel structure of the MC-CDMA based system. It must be noted that the proposed solutions are not limited to MC-CDMA networks but can be easily adapted by other systems with multi channel structure, where multiple channel separation is not necessarily done in code domain.
  • a multihop connection consists of consecutive links, which enable the data transfer between two Mobile Stations (MS)s that cannot establish a direct radio link, and its realization requires the support of the network.
  • a relay function is required, providing the functionality of forwarding MSs, for relaying of data packets to the next node of a multihop connection.
  • Such relay functions can be implemented either in the first, second or third layer of the ISO /OSI reference model.
  • ROADMAP RObust Ack-Driven Media Access Protocol
  • MARCH Multiple Access with ReduCed Handshake
  • ACK implicit Acknowledgements
  • the main focus of the above protocols is multihop support for single channel networks, operating on basis of the IEEE 802.11 Wireless Local Area Network (WLAN).
  • the focus here is the extension of the Medium Access Control (MAC) layer functionality to support packet relaying, in modified Distributed Coordination Function (DCF) for Multi- Carrier Code Division Multiple Access (MC-CDMA) based WLANs.
  • DCF Distributed Coordination Function
  • MC-CDMA Multi- Carrier Code Division Multiple Access
  • Fig. 5 shows the MC-CDMA spreading mechanism with spreading factor 4, as an example.
  • each symbol of the output data stream of a user is multiplied by each element of the user's spreading code.
  • the MC-CDMA chips are formed in this way and placed via Inverse FFT (IFFT) in several narrow band subcarriers. Multiple chips are transmitted in parallel on different subcarriers. This method is called "frequency spreading".
  • IFFT Inverse FFT
  • each user symbol is transmitted in the form of many sequential chips, each of which is of short duration and has a wide bandwidth.
  • FFT Fast Fourier Transform
  • OFDM Orthogonal Frequency Division Multiplexing
  • SF Spreading Factor
  • one subcarrier carries a fraction of the users symbol, and can therefore carry additional load, coming from symbols of other users.
  • a PHY layer of MC-CDMA based DCF is described.
  • orthogonal Walsh Hadamard spreading codes of length 4 are used, obtained from the rows of the 4 th order Hadamard matrix:
  • a CCH is a spreading sequence, which is not explicitly assigned to a MS, but shared among a number of MSs. Each MS considers each spreading sequence as a subchannel of the frequency channel. Consequently, the frequency channel is divided (logically) by the four spreading sequences in four subchannels, the CCHs.
  • MMSE Minimum Mean Square Error
  • ULD Multiuser Detector
  • the rest of the PHY parameters have similar values to the ones used in conventional IEEE 802.1 Ia.
  • the MC-CDMA based DCF is a development of the IEEE 802.1 Ia WLAN MAC protocol, with modifications needed to support the MC-CDMA PHY layer.
  • a MS ready to transmit has to select a cch. Initially this selection is done randomly. For later transmissions, the MS does not select CCHs which have already been reserved by other MSs (according to the standard the considered MS has set a Network Allocation Vector (NAV) for an occupied channel).
  • NAV Network Allocation Vector
  • CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
  • DIFS DCF Interframe Space
  • backoff a MS defers for a certain time, called backoff, before transmitting its packet in order to avoid collisions.
  • the duration of the backoff time is defined by:
  • Random is a uniformly distributed random integer number in interval [0, CW], and aSlotTime equals, for example, 9 ⁇ s.
  • the Contention Window (CW) has a starting value of 7, is doubled after a collision and reduced after a collision resolution.
  • Fig. 6 shows the multichannel approach for the IEEE 802.11 MAC.
  • the MS can initiate data transfer by transmitting a Ready To Send (RTS) packet in the selected codechannel, as depicted in Fig. 6.
  • RTS Ready To Send
  • each MS which receive the RTS frame, and are not the intended receivers, interrupt their backoff down counts and set their NAV.
  • the NAV denotes the time a MS must defer from the medium in order not to interfere with an ongoing transmission.
  • each MS utilizes separate NAV states for each CCH.
  • the intended receiver if idle i.e. able to receive data, responds to the RTS frame with a Clear To Send (CTS) frame, after a time Short InterFrame Space (SIFS).
  • CTS Clear To Send
  • SIFS Short InterFrame Space
  • the SIFS time is mainly the transceiver turnaround time, as each MS is assumed to be equipped with one transceiver.
  • MSs are equipped with four correlators and thus can monitor all four cchs in idle state. Similar to the RTS frame, MSs which receive this CTS set their NAV timer as well.
  • the sender can now transmit its data packet after SIFS.
  • the packet is acknowledged in case of successful reception by an ACK frame, sent from the receiver with a delay SIFS after reception's end. Should two or more MSs access the same cch, on the same frequency channel, at the same time, a collision occurs.
  • a retransmission attempt is started with a new RTS frame after backoff. The above procedure is followed in every codechannel for each data transmission.
  • the number of simultaneous transmissions can be increased until the Signal to Interference and Noise Ratio (SINR) at the receiver decreases to a limit that sets them unable to correctly receive and detect the incoming packets. Therefore, power control plays a major role for the systems capacity.
  • power control is applied by means of an efficient calculation using the RTS and CTS frames.
  • the Smart-Backoff procedure allows a MS to iterate between CCHs during backoff thus directly reduces the delay of a data transfer.
  • MSs applying Smart Backoff monitor all CCHs during backoff and mark the moment a CCH gets idle. If the backoff down count is interrupted one of the three cases shown in Fig. 7 occurs:
  • Another CCH seems idle.
  • the MS has to monitor the CCH for at least a DIFS interval to determine whether it is really idle and then it can continue the down count of backoff timer in this CCH.
  • Another CCH is determined idle and the MS can directly continue its backoff timer down count in this CCH.
  • the MS will choose one of them, preferably the one that is idle for the longer period, for its transmission.
  • the MS can transmit two or more packets in parallel, if after Smart Backoff procedure the correspondent amount of CCHs is idle.
  • Fig. 2 The progress of a multihop connection spanning over 3 hops is shown in Fig. 2.
  • MSl is the initiating node, transmitting data packets over MS2 and MS3 to the final destination MS4.
  • every forwarding MS is responsible for the correct transmission in the next hop, as with its own data.
  • Signalization of the route is done, using the four address fields in MAC overhead as follows:
  • Address 1 Contains the source address of the multihop connection (MSl).
  • Address 2 Contains the next hop (MS2).
  • Address 3 Contains the address of the final receiver. (MS4).
  • Address 4 Contains the address of the second forwarding mobile station (MS3).
  • MS2 signals the correct reception of a data packet, with an ACK, and prepares the transmission to MS3 starting a new backoff.
  • a new backoff is started in MSl too, and a new the transmission between MSl and MS2 would delay the transmission between MS2 and MS3.
  • a multihop guard interval 8 is introduced for MSl (Fig. 3).
  • MSl being the initiator of the multihop connection MSl to MS4, has to provide time for forwarding station MS2 to forward the data packet to MS3. For this reason MSl abstains for an interval, equal to the transmission window duration of the certain data packet.
  • MSl can initiate a transmission according to the carrier sensing rules.
  • MSl can transmit in parallel to MS3 (shown on the bottom left of Fig. 2), using another CCH, which increases overall performance of the multihop connection and reduces the delay.
  • Smart Backoff can be used at transmitting MSs, which enables parallel transmissions. Especially in the case of forwarding MSs serving two multihop connections, like the star topology in Fig. 8. Parallel transmissions at MS3 are essential for achieving lower delays. In such topologies though, Smart or Parallel Backoff might increase the number of collisions.
  • Fig. 8 two multihop transmission take place over the common forwarding MS2: one connection from MSl to MS4 and another from MS3 to MS5.
  • MS3 sets, according to the modified DCF, its NAV timer for the corresponding CCHl upon receiving the RTS frame from MSl (Fig. 3), or the corresponding CTS from MS 2. Smart Backoff would lead MS 3 to another idle CCH (CCH2 in Fig. 3), where it can proceed with backoff count down.
  • a transmission from MS3 would interfere in this case with the ongoing data transfer from MSl to MS2.
  • an extend NAV is proposed, the NAV per CCH and MS.
  • each MS receiving a RTS and/or CTS sets its NAV timer for the denoted duration of transmission, on the channel in which the control frame was received, and marks additionally the involved MS(s) as occupied.
  • This precaution prohibits collisions in multihop scenarios, while it enables Smart Backoff deployment in multichannel networks.
  • a representative multihop scenario is shown in Fig. 9. Besides a bottleneck station MS7, the scenario comprises four multihop connections of 1 to 3 hops. All transmitting MSs are capable of Smart Backoff and parallel transmissions in two CCHs are allowed for MS7, facing highest traffic. The applied values for further simulation parameters are given in Table I.
  • connection between MS2 and MS4 is referred to as con. 1, between MS5 to MS9 as con. 2, between MS6 and MSlO as con. 3 and between MSl 1 and MS12 as con. 4.
  • Fig. 10 presents the carried traffic per connection with the offered load.
  • the one hop con. 1 reaches in saturation the maximum cch MAC level capacity for the applied PHY mode, namely 2.4 Mbit/sec.
  • the 2 hop con. 4 reaches an end-to-end carried traffic of 1.2 Mbit/sec, that corresponds to half the cch capacity.
  • the achieved maximum carried traffic for con. 2 and con. 3 averages to 0.8 Mbit/sec/ for each connection and is limited from the common forwarding station (MS 7), that competes for channel access, prior to every transmission, with one of the two transmitters MS5 and MS6.
  • MS 7 common forwarding station
  • Fig. 11 mean end-to-end queuing delay per connection is shown.
  • the end- to-end queuing delay comprises the queuing delay at all queues for a specific data packet.
  • Results comply with the above throughput analysis: Multihop connections with more hops carry lower traffic and face high end-to-end queuing delay.
  • the direct con. 4 achieves the lowest end-to-end queuing delay (as a direct link), while con. 3 and con. 2 suffer from high end-to-end queuing delay, rapidly raising with offered load.
  • the mean end-to-end queuing delay at saturation load (which is different for every connection), is for all multihop connections approximately the same.
  • Figs. 13 and 14 the CDFs of queuing delay per hop are presented, for 0.75 and 1.25 Mbit/sec offered load per connection, respectively.
  • the offered load is chosen at the saturation point of con. 2 and con. 3, which achieve the lowest carried traffic.
  • the highest queuing delay comprises 200msec for transmissions of MS5. Its queuing delay distribution is similar to the one of MS6, since both MSs are the sources of two multihop connections sharing the same first forwarding station MS7.
  • the multihop guard interval prohibits after a successful data packet transfer the immediate transmission of next data packet, raising the delay of next packets in the queue. Additionally, some collisions occur among MS5 and MS6, which increase further the delay.
  • the second highest queuing delay is achieved by transmissions of MS2, owing to the multihop guard interval for prioritization of forwarding station MS3.
  • the direct link between MSl 1 and MS12 follows, with better queuing delay performance. In this case, queuing delay is affected by the ability of Smart Backoff to detect a free cch.
  • MS6 After its transmission, MS6 (MS5) defers according to the multihop guard interval duration, and MS7 competes for medium access with MS5 (MS6). Should MS5 (MS6) win the competition, MS7 sets its NAV and delays its transmission further, for another 3.1 msec.
  • MS7 to MS8 and MS7 to MSlO The steps on queuing delay diagrams for MS7 (MS7 to MS8 and MS7 to MSlO) give evidence to this situation, which might repeat, up to 3 times.
  • MS8 can transmit concurrently with MS5 in another cch.
  • Fig. 14 the Cumulative Distribution Function (CDF)s of queuing delay per hop are presented, for the case of 1.25 Mbit/sec offered load per connection. Network operation shows the same performance characteristics as in previous case, with the difference of higher queuing delay for MS5 and MS6, which are now in overload. Additionally, data packets at MS2 experience increased queuing delay, with distribution similar to the one of MS6 in Fig. 13, as now the offered load is chosen at the saturation point of MS2 (and not at the saturation point of MS6, as it was the case in Fig. 13).
  • the CDF of end-to-end delay measured as the delay between the arrival of a data packet in the network and the reception of the ACK at the last hop, is depicted in Fig.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

La présente invention concerne une station mobile destinée à un réseau de communication basé sur plusieurs canaux et qui comprend une unité de réception et d'envoi (2) et une unité de commande (4) servant à commander l'unité d'envoi et de réception (2). Ainsi, après la transmission d'informations à une station mobile suivante, un intervalle de garde (8) est inclus pendant lequel aucune information supplémentaire n'est envoyée à la station mobile suivante afin de permettre la transmission de l'information à partir de la station mobile suivante vers d'autres stations mobiles. Dès lors, l'utilisation du réseau de communication est optimisée et le rendement global est augmenté.
PCT/IB2007/051061 2006-03-31 2007-03-27 Station mobile pour un reseau de communication base sur plusieurs canaux Ceased WO2007113730A1 (fr)

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EP06112088 2006-03-31
EP06112088.7 2006-03-31

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Cited By (2)

* Cited by examiner, † Cited by third party
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WO2010003098A3 (fr) * 2008-07-03 2010-05-14 Qualcomm Incorporated Planification de relais opportuniste dans des communications sans fil
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US9078270B2 (en) 2008-07-03 2015-07-07 Qualcomm Incorporated Opportunistic relay scheduling in wireless communications
WO2012110680A1 (fr) * 2011-02-14 2012-08-23 Nokia Corporation Réservation de ressources de transmission dans un réseau sans fil
US9832758B2 (en) 2011-02-14 2017-11-28 Nokia Technologies Oy Reserving transmission resources in wireless network

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