C80216m08_401
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Updated Proposal for Generalized Multi-carrier Support in IEEE 802.16m Systems
Date
Submitted
May 5, 2008
Source(s)
Kamran Etemad (kamran.etemad@intel.com)
Hujun Yin
Sassan Ahmadi
Intel Corporation
Re:
Call for Contributions on Project 802.16m System Description Document (SDD)
Frame structure and control channel structure for multi-carrier operation
Abstract
Stage 2 proposal for a generalized multi-carrier support in IEEE 802.16m systems
Purpose
Discussion and Approval
Notice
Release
Patent
Policy
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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
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Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
1
Updated Proposal for Generalized Multi-carrier Support in IEEE 802.16m Systems
Kamran Etemad, Hujun Yin, Sassan Ahmadi
Intel Corporation
1 Introduction and Background:
The support for multicarrier is a requirement for 802.16m standard. A high level
description of multi-carrier support as it relates to protocol structure has also been
harmonized and adopted in SDD [however the remaining details with respect to
channelization and frame structure impacts need further studies and development. This
contribution presents some technical views and suggestions in scope of SDD to capture
some of the above issues.
The general concepts and solutions presented is also inline with authors ’ earlier
contribution on this topic.
It should be noted that the multi-carrier support in its general sense has relation to other
802.16m features such as inter-frequency HO, load balancing and potentially inter
technology HO. To allow more focused discussion and presentation of this feature we also
suggest the following clarification:
Multi-carrier operation in 802.16m involves the concurrent or semi-concurrent usage of
multiple radio (RF) carriers to improve the QoS support for an MS without completely
transferring the MS’s radio resource, mobility, security and state control management from
one RF carrier to another. The RF carrier which maintains the control of MS is called
Primary carrier. If such transfer is required, the process may be referred to as inter-carrier
load balancing or which may be separately defined as a useful feature.
The current SDD text [1] for multi-carrier allows operation of multiple carriers with different
bandwidths, duplexing of more (or other) radio configurations in contiguous or noncontiguous bands under the same MAC instantiation. It also allows both aggregation (i.e.
concurrent operation) and fast switching (i.e. semi-concurrent operation) between RF
carriers.
2 Frame Structure Considerations for Multi-carrier Operation
The support for multiple RF carriers can be accommodated with the same frame structure
used for single carrier support, however, some considerations in the design of protocol
and channel structure may be needed to efficiently support this feature.
2
Single
Carrier Multicarrier MSs
MSs
Superframe
header
RFC1
Primary
RFC2
Primary
RFC3
Secondary
Superframe
F0
F1
Cntr.
SF
0
F2
F3
Cntr.
SF
1
SF
2
SF
3
SF
4
SF
5
SF
6
SF
7
Figure 1: Multicarrier support in the basic frame structure
In general each MS operating under IEEE 802.16m standard is controlled by one RF
carrier, here in called the primary RF carrier.
When multi-carrier feature is supported, the system may define and utilize additional RF
carriers to improve the user experience and QoS or provide services through additional RF
carriers configured or optimized for specific services.
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 may select and attach to
different primary RF carriers based on their MAC addresses 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.
3 Multi-carrier Operation Principles
The following is common in all modes of multicarrier operation:
 The system defines N standalone RF carriers, each fully configured with all
synchronization, broadcast, common and dedicated control signaling channels.
3






Each MS in the cell is attached and its state being controlled by one of the carriers,
referred to as Primary Carrier for that MS.
The Primary carrier for a user can temporarily utilize radio resources in one or more
of the other carriers, called Secondary Carriers, while maintaining f ull control of MS
mobility, state and context.
Whenever possible, the information about the presence, and timing and
synchronization parameters associated with secondary carriers shall be made
available to the user through the primary carriers. In other words, the MS should
not be required to acquire such information from the secondary carrier.
The resource allocation messages span across multiple RF carriers and also link
adaptation feedback mechanisms would need to incorporate measurements
relevant to both primary and secondary carriers.
The multi-carrier 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.
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 parts of the same spectrum block or in
different non-contiguous spectrum blocks.
There are two approaches to channelization for multicarrier support, either or both of
which can be used in the same deployment.
Scenario 1: All carriers in the system are fully configured to operate standalone and may
support some users as their primary carrier.
Scenario 2: In this case, in addition to fully configured and standalone RF carriers the
system also utilizes additional supplementary radio carriers optimized as data pipes for
certain services or traffic types using limited control signaling capability. Such
supplementary carriers may be used only in conjunction with a Primary Carrier and cannot
operate standalone to offer 802.16m services.
The multiple RF carriers can also be used using aggregation or fast switching.

Aggregation mode: The MS maintains its Radio and PHY layer connection with the
Primary Carrier even while it is receiving data from secondary carrier(s). This multicarrier 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.
This mode requires MS to implement multiple radio
modules. In this case the primary carrier manages the MS state and context similar
to a single carrier mode. The main difference is the allocation messages span
across multiple radio carriers and also link adaptation feedback mechanisms would
need to incorporate measurements relevant to both primary and secondary carriers.

Fast Switching Mode: The MS may interrupt its Radio and PHY layer connection
with the Primary Carrier while it is receiving data from secondary carrier(s). This
mode does not require MS to implement multiple radio modules. In this case there
is need for special design considerations to ensure the primary carrier can maintain
4
control of the MS state and context, despite MS’s temporary absence from the
Primary carrier. Such special considerations include Return-to-Primary timers
and/or broadcast notifications on the secondary carriers to command MS to return
to primary carriers to maintain its logical connections and control by the BS.
The secondary IEEE 802.16m RF carrier should also include all in-band PHY level
feedback mechanisms, such as CQICH and H-ARQ ACK/NACK for allocations on
that carrier. The position of such feedback channels will be allocated explicitly or
implicitly by the primary RF carrier.
.
The Primary Carrier may send configuration
and synchronization about the secondary
carrier.
The Traffic Allocation may point
to data regions in second carrier only or both
primary and secondary carriers if aggregation is
used..
Feedback
Channels
BCCH
(e.g. FCH,
SFH, etc.)
Primary
RF Carrier
MAP
(Resource
Allocation)
Data Burst
Part 1
SF1
SF2
SF3
Feedback Channels carrying ACK/NACK,
Link adaptation Measurement may be sent
on the secondary carrier.
...
SF8
Feedback
Channels
BCCH
(e.g. FCH,
SFH, etc.)
Fast Notification
Signaling
Secondary
RF Carrier
Data Burst
Part 2
Fast Notification Messaging May be sent
on the secondary carrier to direct MS to return
to Primary carrier when needed.
SF1
SF2
SF3
...
SF8
Figure 2: Impact of Multi-carrier on Control/Signaling Messages and Channels, where
BCCH and MAP denote the broadcast control and control and signaling channels,
respectively.
The multicarrier scheme can be used for a mix of different terminals with different
capabilities as follows:




Terminal
Terminal
time
Terminal
Terminal
time
type 0: Legacy devices, no multiple RF carriers support (baseline)
type 1: Single contiguous band, Multiple RF Carriers but Single Carrier at a
type 2: Single contiguous band, Multiple RF Carrier Device (TX and/or RX)
type 3: Multiple non-contiguous bands, RF Carriers but Single RF Carrier at a
5

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
over the same carrier in which data is sent. Alternatively and if multiple simultaneous
carriers 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 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 self-contained 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 RF 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.
4 Multi-carrier
Operation
Considerations
in
Control
Channel
Structure
The following are the basic functional design requirements on channelization to support
multicarrier operation.
 On the Primary Broadcast Channels:
The Primary Broadcast Channels here broadly refer to all synchronization and
broadcast control and signaling channels used for delivering system parameters to the
users in the system.
 Synchronization Channel: Depending on the design of terminal RF front -end
and baseband processing, the preamble (or the synchronization channel) may
be included only on the primary RF carrier. The use of separate synchronization
channels on each RF carrier would be 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, path loss, and DL
synchronization may not be feasible using a single synchronization channel and
use of separate per-carrier synchronization channels may be necessary.
 Broadcast Control and Signaling Channel: To indicate multicarrier support as
well as the presence and parameters associated with secondary carriers. This
information should include:
– Full description of the serving (Primary) Carrier, same as single carrier mode
6
– Indication of Multicarrier Support
– Secondary carrier(s) parameters and configuration
– Parameters Common with the Primary, these may be implicitly signaled
to reduce the overhead.
– Parameters different than Primary, e.g. frequency index/offset, etc.
– Scanning and Switching Rules, Intervals/Durations/Triggers: this information
may also be send unicast depending MS capabilities and type of traffic
supported.

On Common Control and MAP/ Resource Allocation Messages/channels:
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 may be persistent with associated return 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 would be used only for MS’s supporting aggregation.
– Scanning and Switching Rules, Intervals/Durations/Triggers: if different than
general parameters broadcast by the BS.

On Dedicated/Associated Signaling channels:
While receiving data on the secondary carrier the associated feedback signaling such
as HARQ ACK/NAK, Channel Quality measurement, or other fast link adaptation
signaling may be sent on the secondary carrier unless aggregation mode is used.
Notification Channels: The BS may use fast notification channels in the secondary
carrier to direct the user to return to primary carrier for some time critical updates or
communications.

5 Proposed Text for SDD
Insert the following text into Section 11.4.3:
------------------------------- Text Start --------------------------------------------------The support for multiple RF carriers can be accommodated with the same frame structure
used for single carrier support, however, some considerations in the design of protocol
and channel structure may be needed to efficiently support this feature.
7
Single
Carrier Multicarrier MSs
MSs
Superframe
header
RFC1
Primary
RFC2
Primary
RFC3
Secondary
Superframe
F0
F1
Cntr.
SF
0
F2
F3
Cntr.
SF
1
SF
2
SF
3
SF
4
SF
5
SF
6
SF
7
Figure 11.4.x: Multicarrier support in the basic frame structure.
In general, each MS operating under IEEE802.16m standard is controlled by one RF
carrier, called the Primary RF Carrier.
When multi-carrier feature is supported the system may define and utilize additional RF
carriers to improve the user experience and QoS or provide services through additional RF
carriers configured or optimized for specific services.
When the number of users in a sector is large, the system may define multiple primar y 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 identifica tion
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 IEEE 802.16m system compliant RF carriers (i.e. the primary and the secondary RF
carriers) when deployed as adjacent carriers should be aligned at super-frame, frame,
and sub-frame boundaries. Additional requirements on RF carrier spacing may also be
imposed to allow optimized reuse of guard subcarriers for data allocation.
------------------------------- Text End --------------------------------------------------8
Insert the following text into Section 19.1:
------------------------------- Text Start ---------------------------------------------------
19.1 Multi-carrier operation Principles
The following is common in all modes of multi-carrier operation:
 The system defines N standalone RF carriers, each fully configured with all
synchronization, broadcast, and common and dedicated control signaling channels.
Each MS in the cell is attached and its state being controlled by one of the carriers,
referred to as Primary Carrier for that MS.
 The Primary carrier for a user can temporarily utilize radio resources in one or more
of the other carriers, called Secondary Carriers, while maintaining full control of MS
mobility, state and context.
 When available, the information about the presence, and timing and
synchronization parameters associated with secondary carriers shall be made
available to the user through the primary carriers. In other words, the MS should
not be required to acquire such information from the secondary carrier.
 The resource allocation messages span across multiple radio carriers and also link
adaptation feedback mechanisms would need to incorporate measurements
relevant to both primary and secondary carriers.
 The multi-carrier 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.
 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.
There are two approaches to channelization for multicarrier support, either or both of
which can be used in the same deployment.
Scenario 1: All carriers in the system are fully configured to operate standalone and may
support some users as their primary carrier.
Scenario 2: In this case, in addition to fully configured and standalone RF carriers the
system also utilizes additional supplementary radio carriers optimized as data pipes for
certain services or traffic types using limited control signaling capability. Such
supplementary carriers may be used only in conjunction with a Primary Carrier and cannot
operate standalone to offer 802.16m services.
The multiple carriers can also be used using aggregation or fast switching.

In aggregation mode the MS maintains its Radio and PHY layer connection with the
Primary Carrier even while it is receiving data from secondary carrier(s). 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. In this case the primary carrier manages the MS state and
context similar to a single carrier mode. The main difference is the allocation
9
messages span across multiple radio carriers and also link adaptation feedback
mechanisms would need to incorporate measurements relevant to both primary and
secondary carriers. This mode requires MS to implement multiple radio modules
and thus may only be considered for high end device classes.

In the fast Switching Mode: The MS may interrupt its Radio and PHY layer
connection with the Primary Carrier while it is receiving data from secondary
carrier(s). In this case there is need for special design considerations to ensure the
primary carrier can maintain control of the MS state and context, despite MS’s
temporary absence from the Primary carrier. Such special considerations include
Return-to-Primary timers and/or broadcast notifications on the secondary carriers to
command MS to return to primary carriers to maintain its logical connections and
control by the BS. This mode does not require MS to implement multiple radio
modules and thus should be considered as baseline mode.
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.
.
The Primary Carrier may send configuration
and synchronization about the secondary
carrier.
The Traffic Allocation may point
to data regions in second carrier only or both
primary and secondary carriers if aggregation is
used..
Feedback
Channels
BCCH
(e.g. FCH,
SFH, etc.)
Primary
RF Carrier
MAP
(Resource
Allocation)
Data Burst
Part 1
SF1
SF2
SF3
Feedback Channels carrying ACK/NACK,
Link adaptation Measurement may be sent
on the secondary carrier.
...
SF8
Feedback
Channels
BCCH
(e.g. FCH,
SFH, etc.)
Fast Notification
Signaling
Secondary
RF Carrier
Data Burst
Part 2
Fast Notification Messaging May be sent
on the secondary carrier to direct MS to return
to Primary carrier when needed.
SF1
SF2
SF3
...
SF8
Figure 19.1.x: Impact of Multi-carrier on Control/Signaling Messages and Channels
The multicarrier scheme can be used for a mix of different terminals with different
capabilities as follows:
10





Terminal
Terminal
time
Terminal
Terminal
time
Terminal
RX)
type 0: Legacy devices, no multiple RF carriers support (baseline)
type 1: Single contiguous band, Multiple RF Carriers but Single Carrier at a
type 2: Single contiguous band, Multiple RF Carrier Device (TX and/or R X)
type 3: Multiple non-contiguous bands, RF Carriers but Single RF Carrier at a
type 4: Multiple non-contiguous bands, Multiple RF Carrier Device (TX and/or
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
over the same carrier in which data is sent. Alternatively and if multiple simultaneous
carriers 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 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 self-contained 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 RF 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 --------------------------------------------------Insert the following text into Section 10.x:
------------------------------- Text Start ---------------------------------------------------
10.x Multi-carrier Operation Considerations in Control Channel Structure
The following are the basic functional design requirements on channelization to support
multicarrier operation.
 On the Primary Broadcast Channels:
The Primary Broadcast Channels here broadly refer to all synchronization and
broadcast control and signaling channels used for delivering system parameters to the
users in the system.
11

Synchronization Channel: Depending on the design of terminal RF front-end
and baseband processing, the preamble (or the synchronization channel) may
be included only on the primary RF carrier. The use of separate synchronization
channels on each RF carrier would be 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.
 Broadcast Control and Signaling Channel: To indicate multicarrier support as
well as the presence and parameters associated with secondary carriers. This
information should include:
– Full description of the serving (Primary) Carrier, same as single carrier mode
– Indication of Multicarrier Support
– Secondary carrier(s) parameters and configuration
– Parameters Common with the Primary, these may be implicitly signaled
to reduce the overhead.
– Parameters different than Primary, e.g. frequency index/offset, etc.
– Scanning and Switching Rules, Intervals/Durations/Triggers: this information
may also be send unicast depending MS capabilities and type of traffic
supported.

On Common Control and MAP/ Resource Allocation Messages/channels:
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 may be persistent with associated return 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 would be used only for MS’s supporting aggregation.
– Scanning and Switching Rules, Intervals/Durations/Triggers: if different than
general parameters broadcast by the BS.

On Dedicated/Associated Signaling channels:
While receiving data on the secondary carrier the associated feedback signaling such
as HARQ ACK/NAK, Channel Quality measurement, or other fast link adaptation
signaling may be sent on the secondary carrier unless aggregation mode is used.
Notification Channels: The BS may use fast notification channels in the secondary
carrier to direct the user to return to primary carrier for some time critical updates or
communications.

------------------------------- Text End ---------------------------------------------------
12
6 References
[1] IEEE C80216m-07/003r1, “Draft Table of Content for the IEEE 802.16m System
Description Document”, March 2008.
[2] IEEE C80216m-07/282r3, Updated Proposal for IEEE 802.16m System Architecture
and Protocol Structure”, March 2008.
13