Grid-of-Beams (GoB) Downlink Multi-User MIMO
Document Number: IEEE S802.16m-08/487
Date Submitted: 2008-05-09
Source:
Stephan SAUR, Hardy HALBAUER,
Andreas RUEEGG, Frank SCHAICH
Alcatel-Lucent
E-mail:
{Stephan.Saur, Hardy.Halbauer, Andreas.Rueegg,
Frank.Schaich}@alcatel-lucent.de
Venue: Macau, China
Base Contribution: IEEE C80216m-08_487.doc
Purpose: Discuss and adopt this proposal into the 16m SDD
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Motivation
– Several users share one DL radio resource in time and frequency in order to
increase the mean cell throughput
– Multi-user scheduling (user grouping) aims in minimizing the intra-cell
interference
– Application in systems with low frequency reuse factor requires inter-cell
interference mitigation in parallel
– Target: Design of DL MU-System with low complexity that maintains the
capability of inter-cell interference coordination
– Idea: Define a limited set of possible precoding vectors (e.g. 8 vectors) such
that
• vectors build up a Grid-of-Beams (GoB)
• intra-cell interference is minimal for certain combinations of beams
Concept Description
Base Station
…
user signal d1
Mobile Station #n
GoB
Precoding
P
Channel
H
user signal dN
feedback of desired beam index
SM
Detector
W
user signal dn
Concept Description
#8
#7
#6
#5
#4
#3
#2
#1
– BS assigns each data stream to one beam
(precoding vector)
– Closed-loop mode: MS reports required
beam(s) to BS
– Open-loop mode: BS derives appropriate
beam(s) from UL
– Certain combinations of beams share one
radio resource in time and frequency
without severe intra-cell interference (e.g.
#2 and #6)
– Several options for antenna configurations:
• E.g. linear array of x-pol elements for the
transmission of two independent streams
to one MS with the same beam index
exploiting polarization diversity
Requirements
– Closed-loop mode requires “test signal”, e.g. pilots
dedicated to each beam (precoding vector) in order to
determine that beam, which is received with the
highest power level.
– Closed-loop mode requires feedback channel.
Assuming eight possible beams (precoding vectors),
three uncoded bits per data stream are necessary.
Text Proposal to SDD
------------------------------------Start text proposal-----------------------------------MIMO modes
In 16m, three MIMO modes shall be supported:
Single-BS single-user MIMO (SU-MIMO) […]
Single-BS multi-user MIMO (MU-MIMO)
In downlink, a MU-MIMO scheme based on a limited number of possible precoding vectors
building up a grid of beams with spatial separation shall be supported. This scheme aims in
increasing the mean cell throughput even in cellular systems with low frequency reuse factor. Main
advantage is the capability to support advanced inter-cell interference coordination techniques at the
same time. The proposed scheme exhibits very low complexity and can be applied in both closed
and open loop MU-MIMO. Either one or two data streams can be assigned to one user. The use of
cross-polarized antennas at the base station is recommended.
[…]
Multi-BS MIMO: […]
------------------------------------End text proposal------------------------------------