IEEE C802.16m-07/248r2
Project IEEE 802.16 Broadband Wireless Access Working Group
Title Neighbor BS Coordination via MS
Date 2007-11-07 Submitted
Source(s) Gang Shen, Kaibin Zhang, Wei Ni, Wei Voice: + 86-21-50554550-7167 Zou, Jimin Liu, Shan Jin Fax: + 86-21-50554554 Email: [email protected]
Peretz Feder Voice: +1-973-3866976 Email: [email protected]
Voice: +49-711-82132163 Torsten Fahldieck Email: [email protected] Alcatel-Lucent Email: [email protected] DJ Shyy
MITRE
Re: IEEE 802.16m-07/040 Call for Contributions on Project 802.16m SDD
Abstract To allow MS forward BS’s control information to its neighbor BS
Purpose For 802.16m discussion and eventual adoption for SDD This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It Notice represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, Release and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. The contributor is familiar with the IEEE-SA Patent Policy and Procedures: Patent
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Neighbor BS Coordination via MS Alcatel-Lucent, MITRE
1. Introduction With the technical development targeting IMT-Advance, neighboring BS coordination becomes more and more important and frequent for the exchange of some control information, channel information, request / response messages, etc. This coordination is necessary with enhancement of some existing techniques and the adoption of some new advanced techniques, such as fast handover, network MIMO, collaborative MIMO, interference cancellation, fractional frequency reuse, multicast and broadcast service (MBS). For example, in the handover procedure, the serving BS has to negotiate with neighboring BSs for the potential candidates of target BS to check whether the neighboring BS would like to accept the moving MS or not. The serving BS is required to send pre-notification request message to the neighboring BS with MS static context, and the neighboring BS sends back a response message, including the service level predication, estimated HO time and HO optimization parameters. Upon handover completion, the target BS also sends the serving BS a notification that it is now hosts the MS in order that the serving BS releases the resources allocated to the MS. Another example is neighboring BS coordination for interference cancellation. Some time-frequency scheduling information should be exchanged between neighboring BSs for the purpose of interference cancellation or resource reuse. The strict latency requirement is raised for neighboring BS control coordination. A small latency can reduce possible service interruption and improve the performance. Neighbor BS coordination is also used for emergency scenario.
Neighboring BS coordination for fast handover, interference cancellation…
BS1 BS2 M S MS
Fig. 1 Neighboring BS coordination for control information exchange
In the existing neighboring BS coordination method, control information exchange is exchanged via backbone. For example, neighboring BS exchanges pre-notification request / response messages via backbone for handover. Although backbone is suitable for massive data transmission, the latency for control information exchange between neighboring BS via backbone is not predictable, depending on neighboring BS locations and which NCMS they belong to. The total latency on backbone may include transmitting delay, routing / switching delay, and IP encapsulation / encapsulation delay. And the delay will be much longer if IP routing is involved.
2. Neighbor BS Coordination via MS This document proposes a BS-BS coordination scheme via MS. A MS is located within the overlapped coverage of neighboring BSs, who identify this MS for their coordination. In this method, one BS sends control information to the MS first, and then MS forwards the received control - 2 - - 2 IEEE C802.16m-07/248r2 information to the neighboring BS, as illustrated in Fig.2. Thus the control information exchange is conducted via MS, instead of via backbone with unpredictable routing and latency. The channel for coordination between MS and BS is assigned in advance. It could be dedicated or shared control channel. Exchanged control information may be encrypted, and it is transparent to MS. MS does not decode it to get the data contents. It just simply forwards what it receives from one BS to the designated neighbor. The BS coordination via MS is proposed suitable for short and time-critical information exchange between neighboring BSs. Massive information exchange is still transmitted via backbone. Compared to legacy BS coordination via backbone, the latency of this control information exchange is low and predictable.
Neighboring BS coordination
via MS
Neighbor BS
Serving BS MS
Neighboring BS control message exchange
MS is located in the overlapped coverage area of two BSs MS just simply forwards one BS’s control message to its neighboring BS MS does not decrypt the control message
Fig. 2 Neighboring BS control information exchange via MS
3. Common Control Channel A common control channel is shared by multiple BSs, where MS uplink control message transmission through this common control channel can be monitored and received by multiple BSs, as illustrated in Fig.3. So neighboring BS can easily and quickly get some MS’s information (SINR, HO request …) directly, instead of achieving this information from MS’s serving BS via backbone. The common control channel is used for the MS located within the overlapped coverage area of several BSs. It is established such that a common time- frequency area is shared by multiple involved BSs. It can be taken as an uplink broadcast such that MS broadcast its message to multiple BSs, fully using the signal broadcast feature without extra bandwidth consumption. MS may use the common control channel to unicast the message to one BS, or multicast / broadcast the message to several BSs simultaneously. MS identifies its communication partner in the control message by BS ID. It may identify one, several or all involved BS as the communication target. If a BS receives a message without its own ID as destination, it omits it. Only MS located at the overlapped coverage area of multiple BSs have common control channel, as only this MS can communicate to / from multiple BSs. Different MS may have its own common control channel, or several MSs share one common control channel. Downlink common control channel is also possible, where - 3 - - 3 IEEE C802.16m-07/248r2 neighboring BS may transmit control message to the involved MS.
Common control channel
BS BS
BS
Control message
Fig. 3 Common control channel
4. Example in Fast Handover This section gives a possible improvement of fast handover with the introduction of the common control channel and neighbor BS coordination. Fig.4(a) illustrates the procedure of legacy MS handover. Although MS is located within the coverage and direct communication distance of candidate target BS, its static context and handover intention are still firstly received and forwarded by its own BS. It may cause some unnecessary message exchange and latency between the serving BS and the target BS. Fig.4(a) illustrates a possible improvement with control message exchange using common control channel. MS first transmits HO request with its static context. As this message is transmitted through the common control channel, it can be received by it own BS as well as its neighboring BSs. The neighboring BS who would like to accept the moving MS will feedback a response at once, including the service level predication, estimated HO time and HO optimization etc. MS gets the feedbacks from other BSs, and evaluates its handover targets. And then sends its handover preference as well as neighboring BS feedback information to its serving BS. The serving BS responds HO -Rsp to MS, and sends a notification message for handover.
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MS Serving BS Target BS
MOB_MSHO_REQ HO pre-notification request
Possibly experience routing, IP encapsulation / decapsulation... HO pre-notification response
MOB_BSHO_RSP
Fig. 4 (a), Legacy handover procedure
MS Serving BS Target BS
MOB_MSHO_REQ
Target BS HO-Req
MOB_MSHO_REQ with target BS feedback
MOB_BSHO_RSP
Fig. 4 (b), Fast handover with the common control channel and neighbor BS coordination
5. Text Proposal in SDD TOC x.x.x Neighbor BS coordination Neighbor BSs exchange control information for coordination. This coordination information can be forwarded via the MS or RS located in the overlapped coverage area of neighboring BSs. x.x.x Common control channel
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A common control channel is shared by multiple BSs, where the MS or RS exchanges control messages with multiple involved BSs.
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