Link adaptation on aggregated TVWS channels

The availability of Television White Space (TVWS) [1] has attracted considerable attention in industry and academia. Given the relatively small amount of bandwidth allocated to each TVWS channel (e.g., 6, 7 or 8 MHz), and the non-contiguous nature of the availability, channel aggregation ([2], [3]) is an attractive way to make full use of the available TVWS spectrum and achieve higher throughput. In this paper we propose and analyze several link adaptation schemes in the context of MAC layer aggregation. We first analyze the SINR conditions of multiple aggregated channels using a model of a modified 802.11n system that supports TVWS operation. Then, we investigate three different link adaptation mechanisms and compute their MAC layer throughputs. Our results show that the SINR variance on the aggregated channels can be high, mainly due to the unique characteristics of TVWS spectrum, i.e., different maximum transmit powers imposed on different types of TVWS channels, and significant Digital TV (DTV) out-of-band emissions to adjacent TVWS channels. Both analytical and numerical results show that independent link adaptation based on each channel SINR provides much higher throughput than the single adaptation schemes, where a common rate is applied on the aggregated channels.