A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> I. INTRODUCTION <s> The tremendous popularity of wireless systems in recent years has led to the commoditization of RF transceivers (radios) whose prices have fallen dramatically. The lower cost allows us to consider using two or more radios in the same device. Given this, we argue that wireless systems that use multiple radios in a collaborative manner dramatically improve system performance and functionality over the traditional single radio wireless systems that are popular today. In this context, we revisit some standard problems in wireless networking, including energy management, capacity enhancement, mobility management, channel failure recovery, and last-hop packet scheduling. We show that a systems approach can alleviate many of the performance and robustness issues prevalent in current wireless LAN systems. We explore the implications of the multi-radio approach on software and hardware design, as well as on algorithmic and protocol research issues. We identify three key design guidelines for constructing multi-radio systems and present results from two systems that we have built. Our experience supports our position that a multi-radio platform offers significant ben-efits for wireless systems. <s> BIB001 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> I. INTRODUCTION <s> Even though multiple non-overlapped channels exist in the 2.4 GHz and 5 GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel. As a result, these networks rarely can fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. This prevents them from being used as an ISP's wireless last-mile access network or as a wireless enterprise backbone network. In this paper, we propose a multi-channel wireless mesh network (WMN) architecture (called Hyacinth) that equips each mesh network node with multiple 802.11 network interface cards (NICs). The central design issues of this multi-channel WMN architecture are channel assignment and routing. We show that intelligent channel assignment is critical to Hyacinth's performance, present distributed algorithms that utilize only local traffic load information to dynamically assign channels and to route packets, and compare their performance against a centralized algorithm that performs the same functions. Through an extensive simulation study, we show that even with just 2 NICs on each node, it is possible to improve the network throughput by a factor of 6 to 7 when compared with the conventional single-channel ad hoc network architecture. We also describe and evaluate a 9-node Hyacinth prototype that Is built using commodity PCs each equipped with two 802.11a NICs. <s> BIB002 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> I. INTRODUCTION <s> To increase the utilization of the available frequency channel space in 802.11-based wireless mesh networks, recent work has explored solutions based on multi-radio stations. This paper reports on our design and experimental study of a distributed, self-stabilizing mechanism that assigns channels to multi-radio nodes in wireless mesh networks. We take a modular approach by decoupling the channel selection decision from the data forwarding mechanism, which makes our solution readily applicable to real-world operation when used with emerging multi-radio routing solutions. We demonstrate the efficacy of our protocol on a real-world, 14-node testbed comprised of nodes, each equipped with an 802.11a card and an 802.11g card. We show via extensive measurements on our testbed that our channel assignment algorithm improves the network capacity by 50% in comparison to a homogeneous channel assignment and by 20% in comparison to a random assignment. <s> BIB003
The recent proliferation of wireless system has prompted the commoditization of RF transceivers whose prices have rapidly diminished in the past decade. As a result, it becomes feasible to employ multiple inexpensive wireless transceivers in a wireless device, and this can be traced to the development of multi-channel multi-radio ad hoc/mesh networks. For instance, Raniwala and Chieuh BIB002 proposed a multi-channel wireless mesh network architecture called Hyachinth which equips each mesh node with multiple 802.11 network interface cards. However, the fact that each node equips with multiple transceivers imposes the trade-off between two conflicting objective: channel diversity and node connectivity. The use of multiple radios on one hand offers several non-overlapping channels for radios to operate on. This would improve the parallelism of network flows, thereby improving network capacity. On the other hand, since both sender and receiver must tune to the same channel in order to communicate, the network connectivity may be partitioned into several channel groups as each interface may switch to different channel. Thus, Ko et. al. BIB003 suggested one interface of each multi-radio node should be dedicated to a channel that is common to all nodes. This would ensure the connectivity between neighbors can be preserved. Furthermore, according Design for Separation proposed Balh et. al. BIB001 , it suggests that the control and data traffic should be assigned to different radios and operated in separate space and time. Interestingly, consider the nature of control and data flows in MAC protocols, the control message informs neighbors in vicinity (point-to-multipoints) about the subsequent point-to-point data transmission. Therefore, intuitively, the control separation is a common technique used in multiradio systems. To date, there have been a number of MAC proposals featuring out-of-band control, though the approaches varied from one to another and there is no clear classification between these protocols. Hence, it is important to highlight the use of control separation technique and the improvement that it can achieve. In this paper, we surveyed existing multi-channel MAC featuring control separation and provide a classification of these multi-channel protocols based on their purpose of separation. We then identify the key advantages of each class. In addition, we pinpointed some deficiencies in these protocols which might spark new interests in the future multi-radio multi-channel MAC design. The rest of this paper is organized as follows. Section 2 gives the description of the existing multi-channel MAC protocols. Section 3 summarizes the key features of these protocols and outlines the deficiencies of these MAC protocols. Finally, Section 4 concludes this paper.