Effects of routing algorithms on novel throughput improvement of mobile ad hoc networks

c TÜBİTAK Turk J Elec Eng & Comp Sci, Vol.20, No.4, 2012,  doi:10.3906/elk-1008-723 Effects of routing algorithms on novel throughput improvement of mobile ad hoc networks 1 Barbaros PREVEZE1,∗, Aysel ŞAFAK2 Department of Electronics and Communication Engineering, Çankaya University, Balgat, Ankara-TURKEY 2 Department of Electrical and Electronics Engineering, Başkent University, Ankara-TURKEY e-mails: , Received: 29.08.2010 Abstract A cognitive method called most congested access first (MCAF), minimizing the packet loss ratio and improving the throughput of a multihop mobile WiMAX network, is proposed. MCAF combines both the time division multiple access and the orthogonal frequency division multiple access methods. MCAF additionally uses spectral aid and buffer management methods, which are proposed in this paper, to manage both spectrum access and packets in the buffers. By using these novel methods, real-time video and voice packet transmission is achieved, data packet loss rate is minimized, and the system throughput per node is improved. Effects of fastest path and ant colony routing algorithms on throughput improvement methods are investigated. It is shown that the fastest path routing algorithm provides higher throughput values than the ant colony routing algorithm. Key Words: Throughput, routing, cognitive, 802.16j, multimedia 1. Introduction The idea of cognitive radio (CR) was first presented in [1], where a better way of manipulating protocol stacks by defining radio knowledge representation language (RKRL) was proposed. RKRL was designed to be used by software agents with a higher level of competence, driven in part by a large storage of prior knowledge that may be of a cognitive nature. Mitola gave a description of cognitivity later in [2]. The introduction of cognitivity led to new challenges for the resource allocation and design of WiMAX relay-based systems. Most works in the literature attempted to improve system throughput with the cooperation of primary and secondary users for efficient resource allocation [3,4]. However, there is very little work on the network throughput of multihop 802.16j networks [5]. In order to maximize throughput performance, the authors in [3] proposed a method for flexible channel cooperation, allowing secondary users to freely optimize the use of channels for transmitting their own data along with primary data. ∗ Corresponding author: Department of Electronics and Communication Engineering, Çankaya University, Balgat, AnkaraTURKEY 507 Turk J Elec Eng & Comp Sci, Vol.20, No.4, 2012 In [4], the authors focused on determining the throughput potential of CR for various transmission power levels of the secondary nodes and determining the optimal amount of licensing. However, design of a WiMAX relay-based system and per user throughput improvement was not considered in [3] and [4]. In [5], a study of a transparent mode relay-based 802.16j system performance was described by considering the design of WiMAX relay-based systems. However, only 5% throughput improvement was provided with almost twice the signaling overhead. In comparison, our method provides higher throughput values (up to 36%). In [6], the authors addressed the problem of assigning channels to CR transmissions, assuming one transceiver per CR. They attempted to maximize the number of simultaneous CR transmissions. By decreasing the blocking rates of CR transmissions, 50% throughput improvement was provided for single-hop scenarios, but only 20% improvement was provided for multihop scenarios. In [7], the throughput improvement of an 802.16j network was provided for a fixed number of nodes (N = 6). In [8], simulation results were generalized for arbitrary N values, and the simulation results for a traditional pure system (none of the proposed method is in use) were shown to match the results of [9]. In this paper, we use spectral aid (SA) and buffer management (BM) methods with the proposed most congested access first (MCAF) method to manage packets in buffers and provide effective spectrum sharing in a fair and cooperative way. The throughput of a traditional 802.16j network is evaluated initially for a fixed N value (N = 6) as in [7], and then extended to arbitrary N values. It is shown that real-time packet transmission is achieved, the loss rate of nonreal-time data packets is minimized, and system throughput is improved with each method. Finally, the effects of fastest path and ant colony routing algorithms on throughput improvement are investigated. The proposed methods are shown to lead to throughput improvements in both routing algorithms. The amount of spectral usage is also calculated with and without the bandwidth wastage. The throughput is then calculated for the pure system and compared with those of 3 different works [9-11] that provide the throughput of a unicast system by asymptotic analysis or by simulating the conventional relaying network. The results of probabilistic throughput calculations and simulations for a traditional 802.16j network are confirmed by the theoretical and simulation results reported in the literature. To the best of our knowledge, this is the first analytically confirmed event-driven simulation work for WiMAX relay-based network design that focuses on decreasing the packet loss ratio, improving the throughput per user in a cognitive multimedia network, and investigating the effects of routing algorithms on throughput improvement. 2. Throughput of mobile ad hoc networks 2.1. Throughput analysis The asymptotic throughput per user of a unicast system is given by [9]:   B Bn Ru = N + 2 ln(2)N log2 1 + ρ0 ln(N) dn c (1) P ρ0 = N0 ×B×K × β. Here, B is the used bandwidth, N is the number of active nodes, d c is the cell diameter, n is the path loss exponent, P/N 0 is the signal-to-noise ratio (SNR), K is the channel model constant, and β is the bit error rate (BER)-related value. 508 PREVEZE, ŞAFAK: Effects of routing algorithms on novel throughput improvement of..., The corresponding formula from [10] may be written as: Ru = B × log2 (1 + β × E {Γeff }) , N (2) where Γeff is the average effective SNR and takes the value of P/N 0 when the results of a system are being evaluated. The throughput of conventional relaying used in the simulation study in [11] (one relay can transmit at a time) is given by: BR = FL R OF DM (RS) , m m   SSG2i 1 + + SSG2 i bpsi bpsi bps m  SSG1i i=1 i=1 (3) i=1 where FL is frame length, BR denotes the nominal bit rate (bits/s), SSG is the number of nodes using the individual modulation type, bps is the number of bits that can be allocated to one OFDM symbol, and R OFDM(RS) is the number of OFDM symbols needed. The parameter values of Eq. (3) are determined during the simulation according to the network state. 2.2. Comparative analysis of throughput results The simulation results of [9-11] for the conventional 802.16j system were compared with each other using the same parameters (...truncated)