1. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 1 Channel Bonding versus Channel Aggregation IEEE P802.22 Wireless RANs Date: 2006-07-05 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl 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.patcom@iee.org >

2. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 2 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

3. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 3 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

4. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 4 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:

5. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 5 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

6. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 6 Increased Bandwidth: Capacity Increase Bonded TV channels to get more capacity –Shannon: C = B.log 2 (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.log 2 (1+S/(BNo)) –Capacity still increases as bandwidth is increased

7. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 7 Increased Bandwidth: Capacity Increase Capacity of bonded channels as a given signal power is spread over more channels

8. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 8 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.

9. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 9 Increased Bandwidth: Performance Improvement About 5 – 6 dB gain with channel-bonding over two channels, with same total transmit power.

10. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 10 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

11. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 11 Channel Bonding vs. Channel Aggregation: A PHY Perspective When using channel bonding, the guard band in between channels (Guard Band A ) can be reused On the other hand, a larger guard band is required at the band edges (Guard Band B ) Once the OFDMA parameters are finalized in the spec, we can define Guard Band A and Guard Band B –This will lead to extra capacity (about 10%) for channel bonding over aggregation

12. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 12 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

13. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 13 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. Alert-Window (AW) Contention slots for initial ranging Used by AAS CPEs and by single channel CPEs

14. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 14 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

15. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 15 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

16. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 16 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

17. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 17 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

18. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 18 Channel Bonding vs. Channel Aggregation: A MAC Perspective Evaluate the channel utilization Bonding can offer much better channel utilization, with less overhead

19. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 19 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

20. doc.: IEEE 802.22-06/0108r0 Submission July 2006 Carlos Cordeiro, PhilipsSlide 20 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