Analog Bloom Filter and Contention-Free Multi-Bit Simultaneous Query for Centralized Wireless Networks

In this paper, novel simultaneous query techniques are proposed for wireless networks, which allow the access point (AP) of the network to gather key control information from active nodes in the network at low overhead. The query techniques are based on OFDM, and include the analog bloom filter (ABF), with which active nodes send signals simultaneously on randomly selected subcarriers to inform the AP about their identities, as well as the collision-free multi-bit (CFM) query, with which nodes send signals simultaneously on non-overlapping subcarriers to inform the AP about their queue lengths. Both the ABF and CFM queries require just one OFDM symbol as the response, and therefore incur very low overhead. Based on ABF and CFM, a simple medium access control (MAC) protocol, called Muqmac, is also proposed, with which the AP can obtain the queue states of the nodes and schedule data transmissions in a centralized manner. ABF and CFM are first evaluated with the 802.11n channel model and are shown to achieve desirable performance. Both ABF and CFM, as well as Muqmac, are also implemented on the Microsoft Sora software-defined radio. The experimental results show that after removing some obvious overhead specific to the testbed, the MAC layer throughput of Muqmac is over 75% of the physical layer data rate even under very challenging traffic conditions.