Multibeam Smart Antenna Research Articles

Intelligent Multibeam Transmissions for Mission-Oriented Airborne Networks

By using the multibeam smart antennas (MBSAs), the nodes can form a high-throughput wireless mesh network with concurrent packet delivery in multiple directions. In this paper, a novel medium access control (MAC) scheme is designed for multibeam airborne mesh networks. It has the following two features: First, IEEE 802.11-compatible, interference-minimized channel access via a special two-layer MAC architecture, where the upper-layer MAC supports the concurrent multibeam transmission/reception, and the lower-layer MAC takes advantage of MBSAs; second, adjustment of the parameters of the two MAC layers to support different mission priorities in airborne networks, including the allocation of time slots in the upper layer. The simulation results demonstrate the superior performance of our proposed multibeam MAC protocols.

Adaptive Batch Coding: A Balanced Congestion Control Strategy for Multi-Beam Antenna Networks

Multi-Beam Smart Antennas (MBSAs) achieve concurrent communications in multiple beams, thereby providing higher throughput compared to regular directional antennas. Most of the transport control schemes used today are based on TCP, which is too conservative since it indiscriminately reduces the window size upon any packet loss. The other extremity is the de-congestion control strategy, which abandons both window size control and retransmission, aggressively saturates the network, and compensates packet loss via network coding. To adapt to the features of the MBSA-based networks, this paper proposes a balanced transport control strategy between the above two categories, which is based on the idea of Adaptive Batch Coding (ABC) . The proposed ABC scheme resists random loss through redundant coding and copes with congestion via window shrink and retransmission. Using a cross-layer design (between transport and routing layer), both the coding scheme and the traffic allocation are adaptively adjusted according to network conditions. A customized simulation system has been developed to comprehensively evaluate the performance of the proposed ABC protocol. Experimental results show that the proposed scheme overcomes the drawbacks of those two extremities. It achieves both high throughput and high throughput (under packet loss) in MBSA-based networks.

Channel/Beam Handoff Control in Multi-Beam Antenna Based Cognitive Radio Networks

A novel spectrum handoff scheme, called feature stacking (FEAST) is proposed to achieve the optimal “channel + beam” handoff (CBH) control in cognitive radio networks (CRNs) with multi-beam smart antennas. FEAST uses the online supervised learning based on the support vector machine to maximize the long-term quality of experience of user data. The spectrum handoff uses the mixed preemptive/non-preemptive M/G/1 queueing model with a discretion rule in each beam to overcome the interruptions from the primary users and to resolve the channel contentions among different classes of secondary users (SUs). A real-time CBH scheme is designed to allow the packets in an interrupted beam of a SU to be detoured through its neighboring beams, depending their available capacity and queue sizes. The proposed scheme adapts to the dynamic channel conditions and performs spectrum decision in time- and space-varying CRN conditions. The simulation results demonstrate the effectiveness of our CBH-based packet detouring scheme, and show that the proposed FEAST-based spectrum decision can adapt to the complex channel conditions and improves the quality of real-time data transmissions compared to the conventional spectrum handoff schemes.

QoS Provisioning for Wireless LANs With Multi-Beam Access Point

Recently, the integration of smart antenna technology into existing wireless local area networks (WLANs) has been one of the hot spots of research work. In this paper, we design an IEEE 802.11-compliant medium access control (MAC) protocol, named M-HCCA, that fully takes advantage of multi-beam smart antennas equipped at the access point (AP) to not only boost the overall capacity of a WLAN, but also support quality-of-service (QoS) and power conservation for individual mobile users. Specifically, M-HCCA has the following attractive features: (i) since being a polling-based MAC scheme, M-HCCA can innately conquer the problems induced by carrier sensing or directional signals, including beam-synchronization constraint, receiver blocking problem, and unnecessary defer problem; (ii) M-HCCA achieves high real-time throughput by adaptively adjusting the sector configuration to quickly resolve contention/collision and to increase data transmission parallelism; (iii) M-HCCA employs beam-location-aware polling scheduling to not only solve the beam-overlapping problem and back/side-lobe problem, but also let real-time stations save as much energy as possible; (iv) M-HCCA adopts the mobile-assisted admission control technique such that the AP can admit as many newly streams as possible while not violating QoS guarantees made to already-admitted streams; (v) M-HCCA offers a location updating mechanism to promptly renew the beam-location information of a non-responsive station such that the miss-hit problem can be effectively alleviated. Extensive simulation results show that, in terms of throughput, real-time throughput, and energy throughput, M-HCCA significantly outperforms existing protocols even in uneven station distribution, imperfect beam-forming, and high mobility environments.

IEEE 802.15.4 MAC for clustered WSNs with a directional framework

This paper exploits the directionality in the wireless sensor network (WSN) by using single-beam and multibeam directional antennas. We mount a multibeam smart antenna (MBSA) with a main sink cluster head (CH), whereas other child sink CHs and end devices use single-beam sector antennas. The unique reception and transmission property of these antennas requires a sufficient modification to suit omni mode MAC protocols. We choose IEEE 802.15.4 as the platform for the proposed MAC design and analyse the effects of these antennas on the current superframe structure. We simulate the modified MAC protocol by using the OPNET modeller under varying traffic loads and an increasing number of nodes. We find an increase in network performance in terms of delays and energy consumption and a simultaneous decrease in the level of urgency.

Neighbor initiated approach for avoiding deaf and hidden node problems in directional MAC protocol for ad-hoc networks

In this paper we propose a MAC called "Neighbor Initiated Approach for avoiding Deaf and Hidden node problems in directional MAC protocol for Ad Hoc networks", which takes advantage of the multi beam smart antennas. Through the antenna, a node can simultaneously transmit/receive a packet to/from all the directions around it. Thus the antenna switches itself in transmission and reception mode. In our scheme all transmission and reception will be directional. We discussed the hidden and deaf node problems with directional MAC and proposed the scheme to overcome those shortcomings. Our scheme has been inspired by the IEEE 802.11, which includes a new scheme to inform its neighbors who was deaf due to other communication. Moreover, the simultaneous transmission of the RTS/CTS through it's all beams prevent the hidden node problem. In our scheme the idle nodes stay in reception mode for sensing the channel through its M non overlapping beams, as a substitute of omnidirectional antenna. It prevents the hidden node problem due to asymmetry in gain. We have simulated our scheme by OPNET 16.0, and compared our results with CDR MAC, DMAC and IEEE 802.11 protocols. Our results show that NIADH performs better than that of the existing protocols in majority of the scenarios.

A Low-Complexity Adaptive Multi-Beam Space-Time Receiver for CCI/ISI Cancellation over Frequency Selective MultipathChannels

A space-time (ST) receiver is proposed for combating the cochannel interference (CCI) and intersymbol interference (ISI) in a frequency-selective multipath environment. The scheme involves two stages. First, a set of adaptive beamformers pointed at a prescribed angular sector in space is constructed on an oversampled antenna array, each providing effective suppression of CCI and reception of desired signals. Second, a fractionally-spaced decision feedback equalizer (DFE) follows to eliminate the ISI left in beamformer outputs. In particular, both the beamformers and DFE can be realized in the form of a generalized sidelobe canceller (GSC) with the aid of channel estimation, and partial adaptivity is incorporated for reduced complexity processing and improved convergence. The proposed ST receiver can be employed as a multi-beam smart antenna system which is suitable for cellular communications. Computer simulations demonstrate that it can achieve nearly the same performance as the optimal ST minimum mean square error (MMSE) DFE with a much lower implementation complexity.

Indoor Slotted-ALOHA Protocols Using a Smart Antenna Basestation

In this paper we consider the reverse-linkcapacity performance of indoor Slotted-ALOHA protocolsadapted for use with a multibeam smart antenna (SDMA)basestation. When SDMA is used in this application, the basestation attempts to transmit or receivemultiple packets simultaneously using its antenna array.S-ALOHA protocols are well suited for this purpose sincethey permit simultaneous station transmission more readily compared with conventional LANprotocols such as CSMA. It is assumed that the portablestations have omnidirectional antennas and share asingle radio link to the basestation. Versions of the protocols are considered where initial stationaccess occurs in the data slots directly, and when botha single-beam and multibeam reservation channel is usedprior to data slot access. Two slot allocation algorithms are proposed which can be used withthe reservation channel protocols to dynamically assignportable stations to the data channel. It is shown thatsignificant improvements in system capacity are possible when more sophisticated dynamicslot allocation is employed. In the results presented,we optimize the design of each system to maximize thecapacity achieved. The comparisons thus give an indication of the relative trade-offs betweencapacity and complexity possible in such a system. Ofthe cases considered, multibeam operation in bothreservation minislots and data slots can achieve the highest theoretical capacity. However, we findthat when operating under low SNR, and especially forlong packet lengths, only very marginal improvements incapacity are achieved compared with other methods. This is important to note, since operating thesystem with multibeam minislot contention is expected tobe highly complex due to the difficulties of dynamicacquisition. We find that when packet lengths are less than about 2 kbits, there is verylittle capacity advantage in using a single-beamreservation protocol over multibeam slotted ALOHA(S-ALOHA).