Architecting a High-Capacity Last-Mile Wireless Mesh Network

Despite availability of multiple non-overlapping channels in the 2.4GHz and the 5GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks operate in a single channel. This substantially reduces the bandwidth available to each node due to interference between successive hops on the same path as well as between neighboring paths. Figure 1 depicts the severity of such interference. As a result, conventional single-channel ad hoc network architecture can not be applied to form effective wireless mesh networks (WMNs) that can adequately support the bandwidth requirements of a lastmile wireless broadband access network [3] [4], or a campus-scale wireless backbone [5] [6]. This paper describes our efforts in architecting a novel multi-channel wireless mesh network (WMN), called Hyacinth, that effectively addresses this bandwidth problem by fully exploiting non-overlapped radio channels made available by the IEEE 802.11 standards. Most previous research that aimed to utilize multiple channels in an ad hoc network required modifications to 802.11 MAC protocol [1] [2]. In contrast, Hyacinth architecture works on commodity 802.11 hardware, and requires only system software modifications. Specifically, Hyacinth equips each mesh node with multiple 802.11 NICs (network interface cards), and performs a traffic-aware channel assignment and routing to utilize multiple channels. Our simulations show that equipping each mesh network node with just 2 NICs can boost the network goodput by a factor of 6 to 7 when compared with conventional single-channel ad hoc network architecture. We have also built a preliminary 9-node Hyacinth testbed by using standard desktop PCs each equipped with two commodity 802.11a NICs. Empirical measurements on this testbed show similar performance improvements.