IEEE C802.16x-07/NNN
Project
IEEE 802.16 Broadband Wireless Access Working Group
<http://ieee802.org/16>
Title
Integrated Relay Architecture for IEEE 802.16m Systems
Date
November 12, 2007
Submitt
ed
Source(s) Sassan Ahmadi
e-mail: sassan.ahmadi@intel.com
Intel
Corporation
Jerry Sydir
Hujun Yin
Re:
e-mail: jerry.sydir@intel.com
e-mail: hujun.yin@intel.com
Intel Corporation
Intel Corporation
Call for Contributions on IEEE 802.16m System Description Document
802.16m-07_040
Abstract
Integrated relay architecture and protocol structure proposal for IEEE
802.16m systems
Purpose
For discussion and approval by IEEE 802.16 Working Group
(Consideration of integrated relay for IEEE 802.16m systems)
Notice
This document does not represent the agreed views of the IEEE 802.16 Working Group
or any of its subgroups. It 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.
Release
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IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards
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contribution may be made public by IEEE 802.16.
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
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Further information is located at <http://standards.ieee.org/board/pat/pat-
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IEEE C802.16x-07/NNN
material.html> and <http://standards.ieee.org/board/pat>.
Integrated Relay Architecture for IEEE 802.16m Systems
Introduction
IEEE 802.16m system requirements document (IEEE 802.16m-07/002r4) has
provisioned use of multi-hop relay concept in IEEE 802.16m systems (see Section
8.1 of IEEE 802.16m-07/002r4). This contribution provides a proposal for a
scalable multi-hop relay architecture where mobile stations are aware of presence
of relay stations and the relay functionality is an integral part of the airinterface as opposed to an add-on feature.
Logical Nodes and Interfaces
IEEE 802.16m specifies the air interface for the following nodes:

IEEE 802.16m Base Station (BS) – A base station that implements the base
station functionality of the IEEE 802.16m specification. IEEE 802.16m BSs
supports communications with IEEE 802.16m RSs, IEEE 802.16m MSs, and
IEEE 802.16e MSs.

IEEE 802.16m Relay Station (RS) – A relay station that implements the
relay station functionality specified in the IEEE 802.16m specification. IEEE
802.16m
RSs
support communication
with
IEEE 802.16m
BSs, IEEE
802.16m MSs, and IEEE 802.16e MSs.

IEEE 802.16m MS – An MS which supports the mobile station functionality
specified in the IEEE 802.16m specification.

IEEE 802.16e MS – An MS which supports the mobile station functionality
compliant with the WirelessMAN-OFDMA Reference System, as specified in
IEEE 802.16m System Requirements (IEEE 802.16m-07/002r4).
Figure 1 illustrates the logical interfaces between the IEEE 802.16m nodes. The
IEEE 802.16m BS and IEEE 802.16m RS support legacy IEEE 802.16e MSs via a
legacy IEEE 802.16e link. Support for IEEE 802.16m MSs is provided either
directly by the IEEE 802.16m BS or by the IEEE 802.16m RS via an IEEE
802.16m link. Communications between the
IEEE 802.16m BS and IEEE
802.16m RS and between instances of the IEEE 802.16m RS occurs over an IEEE
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802.16m link.
legacy 802.16e
link
802.16e MS
legacy 802.16e link
802.16m BS
802.16m RS
802.16m
802.16m
link
link
802.16m MS
802.16m
link
Scope of IEEE
802.16m
Figure 1 Logical Interfaces
IEEE 802.16m Multi-hop Relay Topology
Figure 2 illustrates the IEEE 802.16m multi-hop relay topology. The BS is
associated with zero or more RSs and zero or more MSs. The R1, R1’, R1’’, and
R1’’’ interfaces are specified by IEEE 802.16m standard.
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IEEE C802.16x-07/NNN
R1
BS
R6
R8
MS
R1’
R1’’
RS
BS
R6
Access Service Network
Gateway
MS
R1’’’
MS
R1’
RS
Access Service Network
Layer 1 and Layer 2 protocols to be
specif ied by 802.16m st andard
Figure 2 IEEE 802.16m Multi-hop Relay Topology
RSs are not required in every cell. When no RSs are present, the BS operates a
single PMP link to support communications with all of the MSs in the cell.
RSs may be deployed within a sector in order to provide improved coverage in an
area within or beyond the cell. The coverage area provided by RSs is not divided
into sectors.
When RSs are present within a sector, communications between the
BS and MS can occur directly or through one or more RSs.
The topology of the nodes within a sector is a directed acyclic graph with the BS
acting as the one and only source node and the MSs acting as the sink nodes.
Multiple paths between the BS and MSs are possible to support cooperative
transmissions of data from multiple RSs or from the BS and RS.
User data is transmitted between the BS and MS. User data is not permitted to flow
from an MS, through an RS and to another MS. IEEE 802.16m defines an air
interface between the BS and MS and does not specify how communications occur
between MSs.
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Frequency Usage within a Relay-enabled Cell
When RSs are present within a sector, two frequency usage schemes are supported.
The BS and all RSs can use a single frequency channel to support all
communications within the sector. This is referred to as shared channel relay. (In
IEEE 802.16j this is referred to as in-band relay). In this frequency usage model
the stations within the sector collaborate to share the resources of the channel
that is assigned for their collective use.
The BS and RS can also be assigned to use separate instances of frequency
channels to support communications on individual links in the topology. This is
referred to as dedicated channel relay. (In IEEE 802.16j this is referred to as outof-band relay.) In this frequency usage model, the allocation of resources on
individual links is performed by the station (MR-BS or RS) designated to control
the link. Stations that control individual links operating using the dedicated
channel relay model do not collaborate in the assignment of resources even if they
are operating at the same frequency.
The architecture does not limit the number of different frequency channels that
can be assigned to support individual access and relay links (or groups of them)
within a sector.
Duplexing In the Presence of Relay
The IEEE 802.16m specification supports both TDD and FDD duplexing. It is
assumed that a given network is deployed using entirely TDD or FDD duplexing.
When RSs are used in an FDD deployment, downlink communications between
all stations are assigned to the downlink channel and uplink communications
between all stations are assigned to the uplink channel.
Relay Functional Architecture
Relay support in IEEE 802.16m is specified as a single mode. This mode should
be based on one of the relay modes specified in IEEE 802.16j. The specific mode is
for further study.
Relay support in IEEE 802.16m is integrated into the architecture rather than
added on as a second step as was unavoidable in IEEE 802.16j. In IEEE 802.16m,
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IEEE C802.16x-07/NNN
MSs are aware of the presence of RSs and the multi-hop nature of the path
between them and the BS. This awareness allows the MSs to participate in
decisions that involve choices between a single-hop path and a multi-hop path.
For example, with the knowledge of the quality of the multi-hop path between
itself and the BS, the MS can better network entry and handover decisions.
Relay Protocol Architecture
In IEEE 802.16m the protocols are designed to account for the multi-hop nature
of the system. Functions and protocols within IEEE 802.16m are explicitly
classified as hop-by-hop functions/protocols, which are performed independently
on
each
hop
of
a
path
between
the
BS
and
MS
and
end-to-end
functions/protocols, which are performed in a coordinated manner across a path
between the BS and MS. When it is possible, protocols in IEEE 802.16m are
specified in a uniform way across the hops, without dividing the protocols into a
relay link part and an access link part. This reduces the complexity of RS
implementation and allows for greater efficiency. For example, a single header
structure that takes into account both end-to-end and hop-by-hop information
can be used, instead of encapsulating an access link PDU in a relay PDU by
adding a relay header as is currently specified in IEEE 802.16j.
Figure 3 illustrates the IEEE 802.16m protocol stack, showing the separation of
data plane and control plane functions and the separation of end-to-end and
hop-by-hop MAC functions.
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Network Layer
Routing
Radio Resource
Management
Location
management
System
configuration
management
Multi-Carrier
Support
Mobility
Management
Idle Mode
Management
MBS
Self-Organization
Network-entry
Management
Security
management
Connection
Management
Convergence Sublayer
MAC Common Part Sub-layer (Resource Control and Management Functions)
QoS
ARQ
Data Forwarding
MAC Common Part Sub-layer (End-to-End Functions)
MAC Common Part Sub-layer (Hop-by-Hop Functions)
Fragmentation/Packing
Scheduling and
Resource
Multiplexing
Sleep Mode
Management
MAC PDU formation
PHY control
Multi-Radio
Coexistence
Interference
management
Ranging
Link Adaptation
(CQI, HARQ, power
control)
Control
Signaling
Encryption
Data Plane
Control Plane
Physical Layer
Figure 3 IEEE 802.16m Protocol Stack
Data Plane Protocol Model
Figure 4 illustrates the data plane protocol stack in the presence of relay.
Convergence sublayer functions are not implemented on the RS. In general, MAC
functions are implemented on the BS, RS, and MS. MAC functions and protocols
are classified as end-to-end or hop-by-hop. Hop-by-hop functions are performed
in the same way on all of the station types. End-to-end functions are performed
in a coordinated fashion across the BS, RS, and MS. The actions taken by the BS,
RS, and MS are not necessarily identical. For example, the actions taken by the
BS, RS, and MS in setting up a connection are not identical.
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IEEE C802.16x-07/NNN
BS
MAC CPS
MS
CS
CS
RS
E2E MAC
E2E MAC
E2E MAC
Functions
Functions
Functions
HbH MAC
HbH MAC
HbH MAC
Functions
Functions
Functions
Security
Security*
Security
PHY
PHY
PHY
IEEE 802.16m Air-
IEEE 802.16m Air-
Interface
Interface
* Security functions may be limited in certain nodes of the network
that are outside of direct control of the operator (also known as security
zone)
Figure 4 Data Plane Protocol Stack
Control Plane Protocol Model
Control in IEEE 802.16m is centralized within the infrastructure stations (BS
and RSs). For most functions the MS is the slave and the BS and RSs are the
master. Control can be distributed between BS and RSs in one of two ways. Control
can be maintained by the BS (purely centralized model) or control can be
distributed between the BS and RSs (distributed model). The choice of control
model is made individually for the individual control functions that exist in the
control plane. The specific models to be used for specific functions are TBD. Figure
5 illustrates the control plane protocol stack.
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MACCPS
MS
BS
RS
Resource Control &
Management Functions
Resource Control &
Management Functions
Resource Control &
Management Functions
E2E MAC Functions
E2E MAC Functions
E2E MAC Functions
HbH MAC Functions
HbH MAC Functions
HbH MAC Functions
Security
Security*
Security
PHY
PHY
PHY
IEEE 802.16m AirInterface
IEEE 802.16m AirInterface
Certain management messages may be ciphered
Figure 5 Control Plane Protocol Stack
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