In this paper we are concerned with the problem of data forwarding from a wireless body area network (WBAN) to a gateway when body shadowing affects the ability of WBAN nodes to communicate with the gateway. To solve this problem we present a new WBAN architecture that uses two communication technologies. One network is formed between on-body nodes, and is realized with capacitive body-coupled communication (BCC), while an IEEE 802.15.4 radio frequency (RF) network is used for forwarding data to the gateway. WBAN nodes that have blocked RF links due to body shadowing forward their data through the BCC link to a node that acts as a relay and has an active RF connection. For this architecture we design a network layer protocol that manages the two communication technologies and is responsible for relay selection and data forwarding. Next, we develop analytical performance models of the medium access control (MAC) protocols of the two independent communication links in order to be used for driving the decisions of the previous algorithms. Finally, the analytical models are used for further optimizing energy and delay efficiency. We test our system under different configurations first by performing simulations and next by using real RF traces.
Despite the architectural and protocol differences, all the previously described schemes share one common characteristic which is the use of a single RF communication technology. To alleviate the problems of a single technology two different ones can be used. The number of works in this area is quite limited. A communication protocol that uses two technologies was presented in @cite_21 . In that work the authors proposed the use of two different RF bands namely the 433MHz and 2.4GHz. The 433MHz band is used for data aggregation whereas the 2.4GHz band is used for data forwarding to the gateway. Since the range of the 433MHz band is limited to approximately 2 meters around the node it is possible to improve the reliability and energy consumption by reducing the number of nodes competing for the same channel. Still, both links use RF for on-body communications and two independent RF bands are required.
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Achieving multi-gigabit per second data rates, millimeter wave communication promises to accommodate future and current demands for very high speed wireless data transmission. However, the mandatory use of directional antennas brings significant challenges for the design of efficient MAC layer mechanisms. In particular, IEEE 802.11ad for the 60 GHz band lacks omni-directional transmissions and carrier sensing. This prevents stations from overhearing the actions of other stations, the so called “deafness” problem, which substantially impairs the efficiency and fairness of CSMA CA medium access. Most existing solutions to this problem depend on properties of lower frequency bands and thus do not apply to 60 GHz. In this paper, we propose a dual-band MAC protocol combining 60 GHz communication with co-existing 5 GHz interfaces. By broadcasting control messages on 5 GHz frequencies, we solve the deafness problem and can use the 60 GHz band exclusively for high rate data transmission. While our approach occupies air time on the 5 GHz band for control messages, it does achieve a net throughput gain (over both bands) of up to 65.3 compared to IEEE 802.11ad. In addition, our simulation results show an improvement of MAC fairness of up to 42.8 over IEEE 802.11ad. Millimeter-wave communications in the 60-GHz band are considered one of the key technologies for enabling multigigabit wireless access. However, the special characteristics of such a band pose major obstacles to the optimal utilization of the wireless resources, where the problem of efficient client association to access points (APs) is of vital importance. In this paper, the client association in 60-GHz wireless access networks is investigated. The AP utilization and the quality of the rapidly vanishing communication links are the control parameters. Because of the tricky nonconvex and combinatorial nature of the client association optimization problem, a novel solution method is developed to guarantee balanced and fair resource allocation. A new distributed, lightweight, and easy-to-implement association algorithm, based on Lagrangian duality theory and subgradient methods, is proposed. It is shown that the algorithm is asymptotically optimal, that is, the relative duality gap diminishes to zero as the number of clients increases . Recent breakthroughs in wireless communica- tion show that by using new signal processing techniques, a wireless node is capable of transmitting and receiving simultaneously on the same frequency band by activating both of its RF chains, thus achieving full-duplex communica- tion and potentially doubling the link throughput. However, with two sets of RF chains, one can build a half-duplex multi-input and multi-output (MIMO) system that achieves the same gain. While this gain is the same between a pair of nodes, the gains are unclear when multiple nodes are involved, as in a general network. The key reason is that MIMO and full-duplex have different interference patterns. A MIMO transmission blocks transmissions around its receiver and receptions around its transmitter. A full-duplex bi- directional transmission blocks any transmission around the two communicating nodes, but allows a reception on one RF chain. Thus, in a general network, the requirements for the two technologies could result in potentially different achievable throughput regions. This work investigates the achievable throughput perfor- mance of MIMO, full-duplex and their variants that allow simultaneous activation of two RF chains. It is the first work of its kind to precisely characterize the conditions under which these technologies outperform each other for a general network topology under a binary interference model. The analytical results in this paper are validated using software-defined radios. A millimeter wave (mm-wave) communication system provides multi-Gb s data rates in short-distance transmission. Because millimeter waves have short wavelength, transceivers can be composed of large antenna arrays to alleviate severe signal attenuation. Furthermore, the link performance can be improved by adopting precoding technology in multiple data stream transmission. However, the complexity of radio frequency (RF) chains increases when large antenna arrays are used in mm-wave systems. To reduce the hardware cost, the precoding circuit can be jointly designed in both analog and digital domains to reduce the required number of RF chains. This paper proposes a new method of building the joint RF and baseband precoder that reduces the computation complexity of the original precoder reconstruction algorithm and enables highly parallel hardware architecture. Moreover, the proposed precoder reconstruction algorithm was designed and implemented using TSMC 90-nm UTM CMOS technology. The proposed precoder reconstruction processor supports the transmissions of one to four data streams for 8 × 8 mm-wave multiple-input multiple-output systems. The operating frequency of this chip was 167 MHz, and the power consumption was 243.2 mW when the supply voltage was 1 V. The core area of the postlayout result was about 3.94 mm 2 . The proposed processor achieved 4, 4.9, 6.7, and 6.7 M channel matrices per second in four-, three-, two-, and one-stream modes, respectively.