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Efficient routing algorithm is required to transmit data from source to destination by multi-hop transmission in wireless sensor networks. In the multi-hop transmission, multipath routing can be one of the solutions to cope with the traffic congestion and unstable link condition. In this paper, we propose partial multipath routing which does not establish a secondary full routing path but a partial multipath to complement some poor links, and it can enable stable data transmission and reduce the number of nodes in routing path and the required total power compared with conventional multipath routing.

In wireless sensor networks, sensor nodes have a short transmission range and data is transferred from source to destination node using the multi-hop transmission. Sensor nodes are powered by battery and the link qualities are different, and the routing protocol in the wireless sensor network is one of the important technical issues. Multipath routing was proposed to reduce the data congestion and increase data throughput. In the multipath routing, however, each path can be interfered by the other path, and it can aggravate network performance. In this paper, we propose the multipath routing scheme for multi-rate wireless sensor networks. The multipath routing selects transmission paths to minimize transmission delay and path interference.

Cognitive radio (CR) has been proposed to solve the spectrum utilization problem by dynamically exploiting the unused spectrum. In CR networks, a spectrum selection scheme is an important process to efficiently exploit the spectrum holes, and an efficient channel allocation scheme must be designed to minimize interference to the primary network as well as to achieve better spectrum utilization. In this paper, we propose a multichannel selection algorithm that uses spectrum hole prediction to limit the interference to the primary network and to exploit channel characteristics in order to enhance channel utilization. The proposed scheme considers both the interference length and the channel capacity to limit the interference to primary users and to enhance system performance. By using the proposed scheme, channel utilization is improved whereas the system limits the collision rate of the CR packets.

Cognitive radio technology enables us to utilize the extra spectrum which is not used by the primary users by sensing the channel condition. To use such an extra spectrum, spectrum allocation is one of the important issues in the cognitive radio networks. The network is dynamic and the available channels are changeable, and the opportunistic channel allocation is required to use the resource efficiently without interference to the primary networks. In this paper, modified proportional fairness scheduling is proposed for cognitive radio networks to satisfy the both fairness and system throughput, and the modified scheduling was designed to reduce the interference to the primary users.

Channel allocation is one of the important issues in the multichannel transmission. In the cognitive radio networks, channel allocation scheme should be designed to improve spectrum efficiency without interfering with the transmission of licensed users. In this paper, we propose a spectrum hole prediction based channel allocation scheme. The proposed channel allocation scheme, predicts spectrum hole by using the channel success rate, and limit the transmission of secondary user`s data, and it reduces the interference to the primary user. The performance of proposed channel allocation scheme is evaluated by the computer simulation.

— Opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. The proposed protocol’s simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.

opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. A dynamical sensing range as a important parameter introduced to maintain the our protocol performance. The proposed protocol"s simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.

In a mobile ad-hoc network, to establish a stable routing path is one of the important technical issues to transmit data from source to destination by multi-hop transmission. Mobile ad-hoc network has time varying channels, and traffic congestion or unstable link condition can be severe problems. To solve those problems, multipath routing protocols were proposed. Conventional multipath routing, however, requires much more nodes and power consumption. In this paper, we propose partial multipath routing with interference avoidance. The proposed routing does not establish another full routing path but establish a partial multipath to complement some poor links, and the routing paths have enough distance from each other to reduce path interference.

One of the principal disadvantages of multicarrier modulation technique is the sensitivity to the frequency offset introduced by Doppler shift. This frequency offset introduces inter-carrier interference (ICI) among the multiplicity of carriers in the multicarrier modulated signal. However, Doppler spread induced by temporal channel variations can provides another means for diversity. In this paper, we propose a modified multicarrier code division multiple access (CDMA) system to exploit Doppler diversity as well as multipath diversity. The key work of our framework is a canonical time-frequency-based decomposition of the mobile wireless channel into series of independent fading channel. The decomposition naturally leads to a time-frequency generalization of the Rake receiver that exploits both multipath and Doppler diversity.

Dynamically exploiting unused-spectrum, cognitive radio has been proposed to solve spectrum utilization problem. In cognitive radio, it is important to minimize the interference to primary service as well as to provide efficient channel allocation. In this paper, we propose a multi-channel allocation scheme based on spectrum hole prediction. Proposed scheme considered both interference length and channel capacity to limit the interference to primary user as well as to enhance system performance. Simulation results show the proposed scheme improves the system throughput.

In a CR (cognitive radio) network, channel selection is one of the important issues for the efficient channel utilization. When the CR user exploits the spectrum of primary network, the interference to the primary network should be minimized. In this paper, we propose a spectrum hole prediction based channel selection scheme to minimize the interference to the primary network. To predict spectrum hole, statistic properties of primary user`s traffic is used. By using the predicted spectrum hole, channel is selected and it can reduce the possibility of interference to the primary user and increase the efficiency of spectrum utilization. The performance of proposed channel selection scheme is evaluated by the computer simulation.

Channel selection is one of important issues in Cognitive Radio (CR) networks and it is closely related to the channel characteristics and primary user's behavior. In this paper, we proposed a modified proportional fairness scheduling which not only consider the fairness and the throughput but also take the primary user characteristics of each channel into account.

To minimize interference in the primary network is the most important requirement in CR (Cognitive Radio) networks. Channel allocation algorithm should be designed to improve spectrum efficiency without interfering in the transmission of licensed users. In this paper, we propose a spectrum-hole prediction based channel allocation scheme. To predict spectrum hole, statistic properties of primary user's traffic is used. By using the predicted spectrum hole, channel can be selected opportunistically and it can reduce the possibility of interference with the primary user and increase the efficiency of spectrum utilization. The performance of proposed channel allocation scheme is evaluated by the computer simulation.

In this paper, we proposed a new multi-relay selection and power allocation scheme to maximize network lifetime. To maximize network lifetime, it is important to select appropriate relay node for cooperative communication and allocate power fairly among nodes in a network as well as to minimize total transmitted power. In the proposed scheme, the channel condition and residual power information were considered in multi-relay selection and the allocated power is proportional to the residual power, satisfies the required SNR at destination node and minimizes the total transmission power. In this paper, proposed scheme is base on ldquoamplify and forwardrdquo (AF) model. We evaluate the proposed scheme using extensive simulation and simulation results show that proposed scheme obtains much longer network lifetime than the traditional scheme.

The quality of wireless communication links that employ code-division multiple access (CDMA) mainly suffers from user capacity limit caused by multiple access interference (MAI). To reduce the MAI, we propose parallel interference cancellation assisted channel estimation (PICACE) especially for the indoor reverse link and present theoretical results. We use the signal processing worksystem (SPW) simulator for evaluating 2-D linear 1st order Gaussian interpolation. Because each user's signal on the reverse link may experience different channel fading, we propose reference aided data structure to distinguish each user's own signal. The theoretical results illustrate that PICACE can extend the user capacity of CDMA.

In this paper, the performance of a wideband CDMA single-user return link with the diversity reception is investigated by simulation under a realistic LEO (low earth orbit) mobile satellite channel model. Since there are fundamental differences in the channel characteristics between the LEO mobile satellite and terrestrial mobile systems, such as relatively small delay spread and the varying elevation angles, these factors are taken into account for the channel model. Based on this simulation result, we evaluate the total channel capacity for the multi-beam system with the various system parameters, such as the power efficiency of satellite transponder, encoding scheme and EIRP or G/T of antenna, taken into account. It is shown that the different types of diversity techniques can be successfully applied to combat the performance degradation due to the low elevation angle and thus, warrant the high-quality and low-cost implementation.

The multi-carrier CDMA technique is attractive in a wireless communication system. It can support a high rate data transmission with a high spectral efficiency. The MC-CDMA (multi-carrier code division multiple access) receiver which employs a multiple access interference (MAI) canceller is proposed and analyzed. The receiver first demodulates the received signal to produce the initial data and the channel estimates. Based on these channel estimations, the cancellation scheme essentially creates the replicas of the MAI and removes them for the second improved data decision. Using theoretical analysis and simulation, the performance of MC-CDMA with parallel interference cancellation (PIC) is investigated according to the mean square error (MSE) of the channel estimation. The result shows the considerably large improvement in performance, which is attained by the interference cancellation technique. But if channel estimation is not performed accurately, then the effect of interference cancellation may be significantly decreased.