IEEE C80216m-09/0283nnn

Project / IEEE 802.16 Broadband Wireless Access Working Group <
Title / Downlink Multi-BS MIMO PHY amendments for 16m
Date Submitted / 2009-01-07
Source(s) / Dong Li, Keying Wu, …Xiaolong Zhu, Hongwei Yang,…
Alcatel-Lucent Shanghai Bell Co., Ltd. / Voice:+ 86-21-50554550; Fax:+ 86-21-50554554
Mail to:
Re: / IEEE 802.16m-08/053r1Call for Comments and Contributions on Project 802.16mAmendment Working Document: 11.8 DL MIMO
Abstract / This contribution proposes the text for the downlink TBDmulti-BS MIMO in the physical layer.
Purpose / Adopt the proposed text into amendment.To be discussed and adopted by TGm for the 802.16m amendment.
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Downlink Multi-BS MIMO PHY amendments for 16m

Dong Li, Keying Wu, Xiaolong Zhu, Hongwei Yang…

Alcatel-Lucentl Shanghai Bell Co., Ltd.

1Introduction

In the current 16m SDD [1], multi-BS MIMO is accepted as an advanced feature of downlink MIMO. More specifically, the following specification is indicated in Section 11.8.4.1 Multi-BS MIMO:.

“Multi-BS MIMO techniques are supported for improving sector throughput and cell-edge throughput through multi-BS collaborative precoding, network coordinated beamforming, or inter-cell interference nulling. Both open-loop and closed-loop multi-BS MIMO techniques can be considered. For closed-loop multi-BS MIMO, CSI feedback via codebook based feedback or sounding channel will be used. The feedback information may be shared by neighboring base stations via network interface. Mode adaptation between single-BS MIMO and multi-BS MIMO is utilized.”

In addition, multi-BS MIMO is also accepted as advanced antenna technologies for interference mitigation, as seen from Section 20.2 Interference Mitigation using Advanced Antenna Technologies.

This contribution proposes the text for the downlink multi-BS MIMO in the physical layer. Downlink multi-BS MIMO MAC amendments are addressed in another contribution.NNN.

2. Proposed text for amendment working document

------Start of Proposed Amendment Text ------

15.3.8DL MIMO

15.3.8.XMulti-BS MIMO

In addition to the SU-MIMO and MU-MIMO modes previously discussed previously, there isan advanced another MIMO mode -- , Multi-BS MIMO,-- is supported. Multi-BS MIMO can be usedtoenhancesector throughput and cell-edge throughputby employing appropriate Multi-BS MIMO precoding, which can be codebook based or vendor-specificthrough inter-cell interference nulling, multi-BS colloaborativecollaborativeoperative precoding, or closed-loop macro diversity (CL-MD), network coordinated beamforming, etc.The precoding for multi-BS MIMO can be either codebook-based or vendor-specific. The Multi-BS MIMO capaThe Multi-BS MIMO capability can be enabled or disabled during the basic capability negotiation in the network entry.

In Multi-BS MIMO mode, two or more BSs coordinate their transmission waveform jointly serve one or more MSs in the way such that each BS may can sbility is enabled or disabled during the basic capability negotiation in the network entry.

In Multi-BS MIMO mode, two or more ABSs coordinate their transmission waveform such that each ABS can strengthenthe useful signal or weakeninterferencefortowardsthe one or more targetAMSs through deliberatelysteering their precoding matrixesmatrices.The Ainvolved BSs involved in such coordination form theaMulti-BSBS-groupset for multi-BS MIMO for Multi-BS MIMO. For each involved target AMS, there is a servingprimaryABSand one or more coordinatingsecondaryABSs in the Multi-BS BS-setgroup for Multi-BS MIMO. Different ABSs in the Multi-BSBS-setgroup forMulti-BS MIMO may act as the servingprimary BSs for different involved target AMSs.

The Multi-BS MIMO procedure transmission may be initiated by either AMSs or the serving ABS and controlled by the serving ABS when the trigger conditions are satisfied. Based on the scanning report sent by AMSs, the serving ABSmay negotiatewith other neighboringadjacentABSs through backbone network to form establish theaMulti-BSBS-setgroup for Multi-BS MIMO. If successful, the serving ABS shall command the AMS to enter into the Multi-BS MIMO mode and the serving ABS will act as the servingprimaryABS for thiseAMS and other ABSs in the Multi-BS-setgroup as coordinatingsecondaryABSs.

The establishment process of a Multi-BSBS-setgroup for Multi-BS MIMO includes the following coordination functionsFor all the BSs that belong to the BS group for Multi-BS MIMO, the following coordination shall be performed.

All ABSs in the Multi-BS-setgroup shall use the same resource zone, referred to as Multi-BS MIMO zone, The resource allocation for Multi-BS MIMO transmission. A multi-BSMIMO zone shall be restricted to particular resource zone, defined as Multi-BS MIMO zone, which can occupiesy one or multiple downlink subframes in one frequency partition.

The servingprimaryABS shall coordinate with the coordinatingsecondaryABSs about the precoding way towardsfor the involved target AMS.

The servingprimaryABS may share the PMIs with the coordinatingsecondaryABSs, corresponding to their individual precoding way, for codebook-based precoding, or the primary BS may coordinatenegotiate the UL sounding allocation,with secondary ABSs for codebook-based precoding andfor sounding-based precoding, respectively.

The primaryservingABSmay coordinate negotiate with coordinatingsecondaryABSs about the data stream distribution within the BS-group, the stream profile (i.e., the FEC type, modulation type, repetition coding) and the pilot pattern allocation corresponding to each stream.

Once a multi-BS-setgroup for multi-BS MIMO is established, the ABSs within the setgroup can use one of the following techniques to perform multi-BS MIMO transmission.

15.3.8.X.1 Inter-cell interference nulling

Inter-cell interference nulling through multi-BScell coordination aided precoding exploits theany additional spatial degrees of freedom at the secondary ABS to reduce its interference to the target AMS in the neighboring cell. The AMS only receives its traffic data from itsthe primary ABS, so the primary and secondary ABSs can use same or different permutations in the multi-BS MIMO zone. Sounding-based precoding can be used in TDD., and cCodebook based precoding can be used in both TDD and FDD.

When UL sounding is used for TDD, the secondary ABS(s) estimates the channel state information (CSI) of the target AMS in the neighboring cell via theits sounding signal(s). The primary ABS informs the secondary ABSs of the sounding information at the target AMS, including sounding zone allocation, sounding pattern, sounding waveform, etc, such that the secondary ABSs can decode the sounding signal from the target AMS. Then, the secondary ABSs within the multi-BS-set It then selects the precoding matrix for its own user such that the interference towards the target AMS is controlled/nulled.

When codebook-based feedback is used for TDD or FDD, the target AMS firstneeds to estimate the DL CSI from the secondary ABS(s) based on downlink common pilots (such as midamble). It then selects one or morea precoding matrix indexes (PMIs) for the secondary ABS(s) that leads to the least/worst interference, and reports the PMI recommendation/restriction information to the primary ABS. The primary ABS forwards this information to the corresponding secondary ABS via the network interface, which then selects its own precoding matrix taking account of such PMI recommendation/restriction.

15.3.8.X.2 Closed-loop macro diversity

For CL-MD, the ABSs within the multi-BS-setgroup perform joint MIMO transmission to one target AMS. Each ABS performs narrow-band or wide-band single-user precoding to the target AMS independently. Among multiple ABSs, either transmitspatial diversity or spatial multiplexing can be performed. The data traffic intended to the target AMS shall be replicated at all ABSs in the multi-BS-setgroup. The same permutation should be used by all BSs in the multi-BS-setgroup over the multi-BS MIMO zone, similar to the case of MDHO in legacy systems. Sounding-based precoding can be used in TDD., and c Codebook based precoding can be used in both TDD and FDD.

When UL sounding is used for TDD, the primary and secondary ABSs estimate the CSI of the target AMS via theits sounding signal(s), and calculates precoding matrices independently to steer their signal power at the target AMS. The primary ABS informs the secondary ABS(s) of the sounding information at the target AMS, including sounding zone allocation, sounding pattern, sounding waveform, etc, such that the secondary ABS(s) can decode the sounding signal from the target AMS.

When codebook-based feedback is used for TDD or FDD, the target AMS first estimates the DL CSI of all ABSs within the multi-BS-setgroup. Based on these channel information, it selects PMIs that maximize the received signal powers from the primary and secondary ABSs, respectively, and reports the PMIs to the primary ABS. The primary BS then forwards the PMI to the corresponding secondary ABS via network interface.

15.3.8.X.3 Multi-BS cooperativellaborative precoding

For collaborativeoperative precoding, BSs within the multi-BS-setgroup perform joint MIMO transmission to multiple target AMSs located in different cells. Each ABS performs multi-user precoding towards multiple target AMSs (i.e, SDMA). Each target AMS receives data streams from multiple ABSs in the multi-BS-setgroup. The data traffic intended to each target AMS shall be replicated at all ABSs within the multi-BS-setgroup. The same permutation should be used by all ABSs within the multi-BS-setgroup over the multi-BS MIMO zone. Sounding-based multi-user precoding can be used in TDD., and c Coodebook based multi-user precoding can be used in both TDD and FDD.

When UL sounding is used for TDD, the primary and secondary ABSs estimate the CSI of each target AMS via its sounding signals, and calculates precoding matrices independently through multi-user precoding. The primary ABS informs the secondary ABS(s) of the sounding information at the target AMS, including sounding zone allocation, sounding pattern, sounding waveform, etc, such that the secondary ABS(s) can decode the sounding signal from the target AMS.

When codebook-based feedback is used for TDD or FDD, each target AMS first estimates the DL CSI of all ABSs within the multi-BS-setgroup. Based on these channel information, it selects PMIs that maximize the received signal powers from the primary and secondary BSs respectively, and reports the PMIs to the primary BS. The primary BS then forwards the PMI to the corresponding secondary ABS via network interface.

------End of Proposed Amendment Text ------

References

[1]IEEE 802.16m-08/003r6, “The Draft IEEE 802.16m System Description Document”