July 2006

Carlos Cordeiro, Philips

Slide 1

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding versus Channel Aggregation

IEEE P802.22 Wireless RANs Date: 2006-07-05

Name Company Address Phone email Carlos Cordeiro Philips USA 914-945-6091 Carlos.Cordeiro@philip

s.com

Monisha Ghosh Philips USA 914-945-6415 Monisha.Ghosh@philips.com

Authors:

Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any 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; 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 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org.>

July 2006

Carlos Cordeiro, Philips

Slide 2

doc.: IEEE 802.22-06/0108r0

Submission

Introduction

• The purpose of this presentation is to compare the Channel Bonding and Channel Aggregation techniques with respect to the following evaluation criteria:– FRD satisfyability– Increased bandwidth– Impact on RF– Impact on PHY– Impact on MAC– Practical Issues

• In this presentation we show that for contiguous channels, channel bonding is the best technical solution– Channel aggregation cannot (does not make sense to) operate over adjacent

channels

July 2006

Carlos Cordeiro, Philips

Slide 3

doc.: IEEE 802.22-06/0108r0

Submission

Outline

• Background

• Review of FRD

• Increased Bandwidth– Theoretical Capacity

– Simulation Results

• Channel Bonding vs Channel Aggregation– An RF Perspective

– A PHY Perspective

– A MAC Perspective

• Practical Issues

July 2006

Carlos Cordeiro, Philips

Slide 4

doc.: IEEE 802.22-06/0108r0

Submission

Background

• Channel bonding is for contiguous channels only

• Thus, for a fair comparison between channel bonding and channel aggregation, only contiguous channels shall be considered

• Throughout this presentation, the following scenario, referred to here as the Comparison Scenario, is used:

Frequency (TVChannel)

TV Channel X-1

Guard BandA

TV Channel X

Guard BandA

TV Channel X+1

Guard BandA

Frequency (TVChannel)

TV Channel X-1 TV Channel X

Guard BandB

TV Channel X+1

July 2006

Carlos Cordeiro, Philips

Slide 5

doc.: IEEE 802.22-06/0108r0

Submission

Review of FRD

• “The typical range of the system is 33 km (based on 4 Watt CPE EIRP and 50% location availability at the edge of the coverage area for a median location and 99.9% time availability F(50, 99.9))”

• “The required minimum peak throughput rate at edge of coverage SHALL be 1.5 Mbit/s per subscriber in the forward direction and 384 kbit/s per subscriber in the return direction”

July 2006

Carlos Cordeiro, Philips

Slide 6

doc.: IEEE 802.22-06/0108r0

Submission

Increased Bandwidth: Capacity Increase

• Bonded TV channels to get more capacity– Shannon: C = B.log2(1+S/N)– Capacity proportional to BW, but logarithmic with SNR or signal

power

• If S/N is fixed, then capacity increases linearly with bandwidth.

• If signal power is fixed, but bandwidth is increased– C = B.log2(1+S/(BNo))– Capacity still increases as bandwidth is increased

July 2006

Carlos Cordeiro, Philips

Slide 7

doc.: IEEE 802.22-06/0108r0

Submission

Increased Bandwidth: Capacity Increase

• Capacity of bonded channels as a given signal power is spread over more channels

July 2006

Carlos Cordeiro, Philips

Slide 8

doc.: IEEE 802.22-06/0108r0

Submission

Increased Bandwidth: Simulation Scenario• 6 MHz System:

– 2048-FFT– 32 users, each with 64 carriers, all assumed to be data. Distributed

subchannelization and interleaving over 6 MHz.– Cyclic Prefix Length: 512

• 12 MHz System– 4096-FFT– 32 users, each with 128 carriers, all assumed to be data. Distributed

subchannelization and interleaving over 12 MHz.– Cyclic Prefix Length: 1024

• Channel: Exponentially faded Raleigh channel with 7 s rms delay spread (total delay spread: 70 s).

• Both systems have same multipath protection, and will be compared based on same data-rate.

July 2006

Carlos Cordeiro, Philips

Slide 9

doc.: IEEE 802.22-06/0108r0

Submission

Increased Bandwidth: Performance Improvement

About 5 – 6 dBgain with channel-bonding over two channels, with same total transmit power.

July 2006

Carlos Cordeiro, Philips

Slide 10

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: An RF Perspective

• In case of channel aggregation– Given the lack of appropriate isolation, the

transmission through channel X may cause RF problems in channels X-1 and X+1

• When channel X is transmitting, channels X-1 and X+1 cannot receive, and vice-versa

• Synchronized is needed – major problem!

– Such very tight synchronization is likely impossible in practice

• Randomness in traffic, real-time, beyond the scope of IEEE 802 (above MAC)

– Major incumbent protection issue: if channel aggregation is done at CPEs, it can violate incumbent protection (more info later)

• These issues are not encountered when channel bonding is used

Frequency (TVChannel)

TV Channel X-1

Guard BandA

TV Channel X

Guard BandA

TV Channel X+1

Guard BandA

Frequency (TVChannel)

TV Channel X-1 TV Channel X

Guard BandB

TV Channel X+1

July 2006

Carlos Cordeiro, Philips

Slide 11

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A PHY Perspective

• When using channel bonding, the guard band in between channels (Guard BandA) can be reused

• On the other hand, a larger guard band is required at the band edges (Guard BandB)

• Once the OFDMA parameters are finalized in the spec, we can define Guard BandA and Guard BandB

– This will lead to extra capacity (about 10%) for channel bonding over aggregation

Frequency (TVChannel)

TV Channel X-1

Guard BandA

TV Channel X

Guard BandA

TV Channel X+1

Guard BandA

Frequency (TVChannel)

TV Channel X-1 TV Channel X

Guard BandB

TV Channel X+1

July 2006

Carlos Cordeiro, Philips

Slide 12

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• Facts:– Channel bonding incurs no additional overhead as all control messages

are transmitted only once– With channel aggregation, the overhead increases considerably with the

number of channels used– For an effective channel aggregation solution, features such as

sophisticated scheduling, load balancing, channel management, etc., are needed

• High cost and complexity– With channel bonding, the BS and CPE have much greater control and

freedom on resource allocation, transmit power, etc.• Implementation is much simplified

• From the MAC perspective, channel bonding is a much superior technical solution

July 2006

Carlos Cordeiro, Philips

Slide 13

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• The MAC can simultaneously support single channel and multi-channel CPEs– Capacity as

needed (up to subscriber)

– Product differentiation

– Controllable by BS, etc.

Superframe n-1 Superframe n Superframe n+1 ...Time

...

Preamble SCH frame 0 frame 1 frame m...

Unit Channelt-1

Unit Channelt

Unit Channelt+1

Time

Preamble SCH

Preamble SCH

Frequency

Preamble SCHFrame

0Frame

1Frame

m... ...Frame

1Frame

0

AW

Frame2

Frame0

Frame2

Frame0

Frame2

Preamble SCH

Preamble SCH

Preamble SCH

AW

AW

AW

Alert-Window (AW)

• Contention slots for initial ranging• Used by AAS CPEs and by single channel CPEs

July 2006

Carlos Cordeiro, Philips

Slide 14

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• The MAC functionality to support channel bonding and aggregation have been implemented in OPNET

• Some simulation parameters– Superframe size = 16 frames, where Frame size = 10 ms

– Packet size = 1 Kbyte

– 64-QAM rate 2/3 and Symbol time = 310 µs

• Our simulation experience– While no change is required to the scheduler for channel bonding support,

the added complexity to the code to support aggregation was substantial

July 2006

Carlos Cordeiro, Philips

Slide 15

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• Evaluate the performance at the MAC SAP under varying number of TV channels

• 1 BS and 127 CPEs

July 2006

Carlos Cordeiro, Philips

Slide 16

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• Aggregation incurs much more overhead than channel bonding

• Aggregation and bonding are designed for medium-high loads, and in these cases bonding clearly surpasses aggregation

Even though the throughput is the same, the overhead is much larger with aggregation

July 2006

Carlos Cordeiro, Philips

Slide 17

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• Evaluate the protocol efficiency of aggregation and bonding

– Protocol Efficiency = (Data bits Rx/Total bits Tx)

• The MAC protocol efficiency with channel bonding outperforms that with channel aggregation

– A consequence of the much lower additional overhead of bonding

July 2006

Carlos Cordeiro, Philips

Slide 18

doc.: IEEE 802.22-06/0108r0

Submission

Channel Bonding vs. Channel Aggregation: A MAC Perspective

• Evaluate the channel utilization

• Bonding can offer much better channel utilization, with less overhead

July 2006

Carlos Cordeiro, Philips

Slide 19

doc.: IEEE 802.22-06/0108r0

Submission

Practical Issues

• Far out CPEs may not be able to be serviced by a BS employing aggregation, but may be serviced by one using channel bonding

• A single customer cannot have more than one CPE in his/her premises, otherwise it will cause harmful interference to nearby TV receivers (as per the 10m separation assumption)

– Therefore, channel aggregation is not possible at the CPE level (even though, in practice, nothing can be done by IEEE 802.22 to avoid it)

– Channel bonding is the only way to offer higher capacity or range at the CPE level

• Channel bonding is a more cost effective than channel aggregation– Does not require additional radios

• Channel bonding is much less complex than channel aggregation– Does not requires a number of other complex features (e.g., load balancing,

sophisticated scheduler, etc.) that are needed with aggregation

July 2006

Carlos Cordeiro, Philips

Slide 20

doc.: IEEE 802.22-06/0108r0

Submission

Conclusions

• For contiguous channels, bonding is a much more technically sound approach– Channel aggregation is not feasible for contiguous channels

• Channel bonding also allows for product differentiation

• We have shown that when considering the FRD, bandwidth, and the impact on RF, PHY, and MAC, channel bonding is the option of choice for contiguous channels