C80216m08_092r1
Project
Title
IEEE 802.16 Broadband Wireless Access Working Group
<http://ieee802.org/16>
Proposal for Generalized Multi-carrier Support in IEEE 802.16m
Systems
Date
Submitt
January 21, 2008
ed
Kamran Etemad (kamran.etemad@intel.com)
Source(s)
Sassan Ahmadi
Hujun Yin
Intel Corporation
Call for Contributions on Project 802.16m System Description
Re:
Document (SDD)
Topic: System Architecture and Protocol Structure
Abstract
Purpose
Stage 2 proposal for a generalized multi-carrier support in IEEE
802.16m systems
Discussion and Approval
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
Notice
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, and any
Release
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;
1
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
Policy
<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
<http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at
<http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
2
Generalized Multi-Carrier Support in IEEE 802.16m Systems
Kamran Etemad, Sassan Ahmadi, Hujun Yin
Intel Corporation
1 Introduction and Background
With the growing demand for mobile broadband data services and
shortage of contiguously large spectrum for deployment, one would expect
the next generation broadband wireless access networks to be deployed
using a combination of different spectrum. Therefore in the near future
multi-band deployments in paired and unpaired spectrum would be a
norm rather than exception.
Also as the systems are deployed and the need for higher data rate grow,
the same technology may be deployed based on wider band RF carriers,
motivating a need to support a combination/concatenation of channel
bandwidths to best fit the available spectrum while enabling data
transmission over multiple carriers.
Considering that IEEE 802.16m technology may be deployed as the
evolution of existing mobile networks or may be deployed in conjunction
with other specialized wireless access technologies such as mobile TV
systems, there is need for the multi-carrier solution to accommodate tight
coupling of IEEE 802.16m and other access technologies. Such tight
coupling will be critical for effective and seamless interworking and
potentially
load
balancing
across
collocated
or
neighboring
access
networks supporting single radio and power efficient devices.
Based on these objectives which are inline with the currently agreed SRD,
this
contribution
generalizes
the
proposes
existing
a
simple
multi-carrier
multi-carrier
concepts
solution
used
in
which
cellular
technologies to mixed RF carrier bandwidths, mix duplexing modes,
or
mixed broadband wireless access technologies. For example the IEEE
802.16m RF carriers can be coupled with 3G RF carriers or mobile video
broadcast RF carriers.
3
Note that this contribution does not address variable bandwidth terminal
support, i.e. supporting MSs with different bandwidths in the same
carrier, which is also a desirable feature for IEEE 802.16m and should
be addressed separately.
2 Description of the Concept
The proposed generalized multi-carrier (MC) scheme would allow the
network to support a mix of different RF carriers deployed in contiguous
or
non-
contiguous
spectrum.
This
scheme
involves
the
following
scenarios:

One or more primary RF carriers with full MAC/Signaling/Control
plane messaging plus user traffic.

One
or
more
secondary
RF
carriers
with
potentially
separate
preambles, notification indicators, as well as the rest of user traffic
and associated PHY/lower MAC signaling such as CQICH and H-ARQ
ACK/NACK. Some or all signaling and MAC messages may also be
transmitted on secondary carriers.
The primary RF carrier(s) is used to provide all broadcast and common
control messaging to the terminals and further controls MS’s
state
transitions, e.g. active to sleep or idle mode.
When the number of users in a sector is large, the system may define
multiple primary RF carriers and define a mechanism to semi-statically
distribute users and their MAC/signaling traffic across multiple primary
carriers. The users can select and attach to different primary carriers
based on their MAC address or other hardware identification numbers or
randomly choose one of available primary carriers. Each user will be
connected to one primary IEEE 802.16m RF carrier at a time.
The primary RF carrier(s) can also direct the MS to move to another
primary RF carrier if needed.
4
The secondary RF carrier(s) which is usually but not necessarily a data
only pipe may have different

Channel bandwidth (e.g. 5, 10, 20, 40MHz),

Duplexing Mode (TDD or FDD),

Spectrum Allocation,

or DL/UL Ratio (e.g. can be DL Multicast-Broadcast only)
compared to the primary RF carrier. The secondary IEEE 802.16m carrier
should also include all in-band PHY level feedback mechanisms, such as
CQICH and H-ARQ ACK/NACK for allocations within that carrier. The
position
of
such
feedback
channels
will
be
allocated
explicitly
or
implicitly by the primary RF carrier.
A primary RF carrier may be dynamically associated with multiple
secondary RF carriers. Multiple primary RF carriers may also share the
same secondary carrier to expand their bandwidth. The multiple carriers
may be in different part of the same spectrum block or in different non contiguous spectrum blocks.
This multi-carrier data aggregation effectively creates virtual wideband
channels with higher peak data rates, while supporting mix of legacy
narrow bandwidth and the new multi-carrier terminals.
The multi-
carrier data aggregation may be used in the downlink and/or uplink
asymmetrically
based
on
system
load
(i.e.,
for
static/dynamic
load
balancing), peak data rate, or QoS demand.
The proposed multi-carrier enhancements also allow static/dynamic load
sharing and fast handover across multiple RF carriers with different
bandwidths and duplexing modes .
5
Freq/
Tones
Network Layer
Broadcast
Messaging/
Indicators
RF2
Scheduling
P
R
E
A
M
B
L
E
MAC/Signlling
PHY
RF1
UL
Allocations
DL Allocations
RF1
Broadcast
Messaging
P
R
E
A
M
B
L
E
PHY
RF2
PHY
RF1
PHY
RF3
PHY
RF1
PHY
RF1
PHY
RF2
PHY
RF3
MAC/Signlling
MAC/Signlling
MAC/Signlling
Scheduling
Scheduling
Scheduling
Network
Layer
Network Layer
Network Layer
User 1
(10MHz)
User 2
(20MHz)
User 3
(20MHz)
Common
Messaging
UL Allocations
DL Allocations
Time
Figure 1: Illustration of the proposed generalized multi-carrier scheme for
TDD duplex scheme.
Figure 1 illustrates the proposed generalized multi-carrier scheme for
TDD duplex scheme. Note that if RF1 and RF2 are adjacent RF carriers,
their corresponding DL/UL sub-frames shall be aligned to reduce intercarrier interference. The alignment of DL/UL sub-frames across nonadjacent RF carriers is not necessary.
Depending
on
processing,
the
included
only
the
design
preamble
on
the
of
(or
terminal
the
primary
RF
front-end
synchronization
RF
carrier.
The
and
channel)
use
of
baseband
may
be
separate
synchronization channels on each RF carrier is necessary, if the terminal
can only process one RF carrier at a time and is not capable of
maintaining synchronization while switching from one RF carrier to
another. In addition, if the RF carriers are far apart in frequency,
channel estimation and DL synchronization may not be feasible using a
single
synchronization
channel
and
use
of
separate
per-carrier
synchronization channels may be necessary.
6
It must be further noted that the proposed multi-carrier support equally
applies to both TDD and FDD systems and use of TDD mode is for example
only.
Using and generalizing the same capability the multi-carrier scheme in
IEEE 802.16m would potentially allow layer 2 coupling of an IEEE
802.16m system with an alternative collocated radio technology deployed
as the secondary RF carrier.
carrier
advertisement,
The layer 2 coupling would support cross-
allocations
and
signaling
to
help
seamless
interworking, handover and load balancing between the systems.
The main features that are required to enable this capability in the airinterface technology, besides hardware support, are the following:

Enhanced Broadcast Channel Configuration Messaging to define a
multi-carrier
channel
configuration
on
the
serving
cell.
This
channel configuration should include:
– Serving and other primary RF carriers’ parameters (if different
than the primary)
– RF Carrier Index,
– RF Carrier parameters (if different than the primary):
Including center frequency,
– Secondary Carriers List, specifying,
– RF Carrier Index,
– Technology Type,
– RF Carrier parameters (if different than the primary):
Including center Frequency, BW, FFT size, Frame Size,
DL/UL ratio, etc.,

Traffic allocations have the flexibility of pointing to data regions in
the primary RF carrier and/or secondary RF carriers.
– Allocation can be made to a single region in the primary RF
carrier or secondary RF carrier and can be persistent with
dedicated timers.
7
– The allocation can also point to multiple data regions across
two/multiple
carriers
at
the
same
or
different
subframes.
Simultaneous allocations across multiple RF carriers

For more effective vertical inter-technology hand off one can also
define and advertise delta channel configuration for all primary
carriers on neighboring BS’s, differences in
– Technology
– Center Frequency
– Channel Size
– Scanning Rules, Intervals/Durations/Triggers
This generalized scheme can be used for a mix of different terminals with
different capabilities as follows:

Terminal type 0: Legacy devices, no multiple RF carriers support
(baseline)

Terminal type 1: Single contiguous band, Multiple RF Carriers but
Single Carrier at a time

Terminal type 2: Single contiguous band, Multiple RF Carrier Device
(TX and/or RX)

Terminal type 3: Multiple non-contiguous bands, RF Carriers but
Single RF Carrier at a time

Terminal type 4: Multiple non-contiguous bands, Multiple RF Carrier
Device (TX and/or RX)
In general, the associated MAC and signaling messages during the data
traffic exchanges; e.g., link adaptation, H-ARQ ACK/NACK and channel
quality feedback may be transmitted in the same carrier in which data is
sent. Alternatively and if multiple simultaneous carrier is supported in
Type 2 and 4, such messages can be combined for all carriers and sent on
the Primary carrier.
To support terminal types 1 and 3, In addition to data and associated
MAC/signaling, the secondary RF carrier will also include notifications to
8
ensure that the devices currently allocated and temporarily operating on
the second RF carrier can be directed back to the primary RF carrier if
there is an urgent message to be delivered to them.
The broadcast notifications on the secondary RF carriers can be binary
indicators to which terminals will hash based on MAC address or selfcontained and dedicated MAC messages. All terminal types 1 and 3 that
are directed to a secondary RF carrier should monitor such broadcast
notification for the frame during which they use that secondary RF
carrier.
When secondary carrier is an alternative radio access technology (RAT)
the allocations on that secondary carrier should include a timer to ensure
return of the MS to the primary carrier. The MS should return to the
primary carrier once the time expires unless asked not to through layer3+
messages on the alternative access technology.
3 Protocol Structure for Multi-carrier Support
A protocol structure was proposed in [2] where the layer 1 and layer 2
functions were classified, depending on their characteristics into data
plane and control plane functions. In addition, layer 2 functions were
further
classified
into
radio
resource
control
and
management
functions and medium access control functions. A generalization of
that protocol structure to multi-carrier support using a single MAC
instantiation is shown in Figure 2. The load balancing functions and
RF carrier mapping and control, discussed in the previous section, are
performed via radio resource control and management functional class.
9
Control
Data Plane
Plane
CS
Radio Resource Control
SAP
CS Sub-Layer
& Management Functions
Data and Control
Bearers
L2
Medium Access Control Functions
Security Sub-Layer
Dynamic/Static
MAC Common Part Sub-Layer
Mapping
PHY 1
Physical
Physical
Physical
Channels
Channels
Channels
PHY 2
PHY n
…
RF Carrier 2
RF Carrier 1
L1
RF Carrier n
Figure 2: Protocol structure for multi-carrier support
4 Proposed Text for SDD
Insert the following text into Support for Multi-carrier sub-clause
(i.e. Chapter 19 in [2]):
------------------------------- Text Start -------------------------------------------------19.0 Generalized Multi-carrier Support in IEEE 802.16m
The IEEE 802.16m generalized multi-carrier scheme would allow the
network to support a mix of different RF carriers deployed in contiguous
or
non-
contiguous
spectrum.
This
scheme
involves
the
following
scenarios:

One or more primary RF carriers with full MAC/Signaling/Control
plane messaging plus user traffic.

One
or
more
secondary
RF
carriers
with
potentially
separate
preambles, notification indicators, as well as the rest of user traffic
and associated PHY/lower MAC signaling such as CQICH and H-ARQ
10
ACK/NACK. Some or all signaling and MAC messages may also be
transmitted on secondary carriers.
The primary RF carrier(s) is used to provide all broadcast and common
control messaging to the terminals and further controls terminals state
transitions, e.g. active to sleep or idle mode.
When the number of users in a sector is large, the system may define
multiple primary RF carriers and define a mechanism to semi -statically
distribute users and their MAC/signaling traffic across multiple primary
carriers. The users can select and attach to different primary carriers
based on their MAC address or other hardware identification numbers or
randomly choose one of available primary carriers. Each user will be
connected to one primary IEEE 802.16m RF carrier at a time.
The primary RF carrier(s) can also direct the MS to move to another
primary RF carrier if needed.
The secondary RF carrier(s) which is usually but not necessarily a data
only pipe may have different

Channel bandwidth (e.g., 5, 10, 20, 40MHz),

Duplexing Mode (TDD or FDD),

Spectrum Allocation,

or DL/UL Ratio (can be DL/Multicast-Broadcast only)
compared to the primary RF carrier. The secondary IEEE 802.16m carrier
should also include all in-band PHY level feedback mechanisms, such as
CQICH and H-ARQ ACK/NACK for allocations within that carrier. The
position
of
such
feedback
channels
will
be
allocated
explicitly
or
implicitly by the primary RF carrier.
A primary RF carrier may be associated with multiple secondary RF
carriers. Multiple primary RF carriers may also share the same secondary
carrier to expand their bandwidth. The multiple carriers may be in
11
different part of the same spectrum block or in different non -contiguous
spectrum blocks.
Freq/
Tones
Network Layer
Broadcast
Messaging/
Indicators
RF2
Scheduling
P
R
E
A
M
B
L
E
MAC/Signlling
PHY
RF1
UL
Allocations
DL Allocations
RF1
Broadcast
Messaging
P
R
E
A
M
B
L
E
PHY
RF2
PHY
RF1
PHY
RF3
PHY
RF1
PHY
RF1
PHY
RF2
PHY
RF3
MAC/Signlling
MAC/Signlling
MAC/Signlling
Scheduling
Scheduling
Scheduling
Network
Layer
Network Layer
Network Layer
User 1
(10MHz)
User 2
(20MHz)
User 3
(20MHz)
Common
Messaging
UL Allocations
DL Allocations
Time
Figure x-1: Illustration of the proposed generalized multi-carrier scheme
for TDD duplex scheme.
Figure x-1 illustrates the proposed generalized multi-carrier scheme for
TDD duplex scheme. Note that if RF1 and RF2 are adjacent RF carriers,
their corresponding DL/UL sub-frames shall be aligned to reduce intercarrier interference. The alignment of DL/UL sub-frames across nonadjacent RF carriers is not necessary.
Depending
on
processing,
the
included
only
the
design
preamble
on
the
of
(or
terminal
the
primary
RF
front-end
synchronization
RF
carrier.
and
channel)
The
use
of
baseband
may
be
separate
synchronization channels on each RF carrier is necessary, if the terminal
can
only
process
one
RF
carrier
at
the
time
and
not
capable
of
maintaining synchronization while switching from one RF carrier to
another. In addition, if the RF carriers are far apart in frequency,
channel estimation and DL synchronization may not be feasible using a
12
single
synchronization
channel
and
use
of
separate
per-carrier
synchronization channels may be necessary.
It must be further noted that the proposed multi-carrier support equally
applies to both TDD and FDD systems and use of TDD mode is for example
only.
The main features that are required to enable this capability in the air interface technology, besides hardware support, are the following:

Enhanced Broadcast Channel Configuration Messaging to define a
multi-carrier
channel
configuration
on
the
serving
cell.
This
channel configuration should include:
– Serving and other primary RF carriers’ parameters (if different
than the primary)
– RF Carrier Index,
– RF Carrier parameters (if different than the primary):
Including center frequency,
– Secondary Carriers List, specifying,
– RF Carrier Index,
– Technology Type,
– RF Carrier parameters (if different than the primary):
Including center Frequency, BW, FFT size, Frame Size,
DL/UL ratio, etc.,

Traffic allocations have the flexibility of pointing to data regions in
the primary RF carrier and/or secondary RF carriers.
– Allocation can be made to a single region in the primary RF
carrier or secondary RF carrier and can be persistent with
dedicated timers.
– The allocation can also point to multiple data regions across
two/multiple
carriers
at
the
same
or
different
subframes.
Simultaneous allocations across multiple RF carriers
13

For more effective vertical inter-technology handoff one can also define
and advertise delta channel configuration for all primary carriers on
neighboring BS’s, differences in
– Technology
– Center Frequency
– Channel Size
– Scanning Rules, Intervals/Durations/Triggers
This generalized multi-Carrier scheme can be used for a mix of different
terminals with different capabilities as follows:

Terminal type 0: Legacy devices, no multiple RF carriers support
(baseline)

Terminal type 1: Single contiguous band, Multiple RF Carriers but
Single Carrier at a time

Terminal type 2: Single contiguous band, Multiple RF Carrier Device
(TX and/or RX)

Terminal type 3: Multiple non-contiguous bands, RF Carriers but
Single RF Carrier at a time

Terminal type 4: Multiple non-contiguous bands, Multiple RF Carrier
Device (TX and/or RX)
In general, the associated MAC and signaling messages during the data
traffic exchanges; e.g., link adaptation, H-ARQ ACK/NACK and channel
quality feedback may be transmitted in the same carrier in which data is
sent. Alternatively and if multiple simultaneous carrier is supported in
Type 2 and 4, such messages can be combined for all carriers and sent on
the primary carrier.
To support terminal types 1 and 3, In addition to data and associated
MAC/signaling, the secondary RF carrier will also include notifications to
ensure that the devices currently allocated and temporarily operating on
14
the second RF carrier can be directed back to the primary RF carrier if
there is an urgent message to be delivered to them.
The broadcast notifications on the secondary RF carriers can be binary
indicators to which terminals will hash based on MAC address or selfcontained and dedicated MAC messages. All terminal types 1 and 3 that
are directed to a secondary RF carrier should monitor such broadcast
notification for the frame during which they use that secondary RF
carrier.
When secondary carrier is an alternative radio access technology (RAT)
the allocations on that secondary carrier should include a timer to ensure
return of the MS to the primary carrier. The MS should return to the
primary carrier once the time expires unless asked not to through layer3+
messages on the alternative access technology.
------------------------------- Text End --------------------------------------------------
5 References
[1] IEEE C80216m-07/320r1, “Draft Table of Content for the IEEE
802.16m System Description Document”, November 2007.
[2] IEEE C80216m-07/282r2, Proposal for IEEE 802.16m System
Architecture and Protocol Structure”, November 2007.
15