The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, we investigate the utility-based resource allocation problem in OFDMA relay networks with service differentiation, where Rate Constraint (RC) and Best Effort (BE) services are supported. Our objective of resource allocation is to maximize the sum utility of BE service users, while guaranteeing that the utility of each RC service user is equal to one. A joint optimization problem for...
In this paper, we investigate the benefits of using cooperative relays in interweave (opportunistic) cognitive radio systems. A novel distributed space frequency (DSF) code for relay cooperation is presented. The code is designed to be a multi-user multi-OFDM channels code. It achieves a cooperative diversity gain of order NL for all users, where N is the number of relays and L is the number of paths...
In this paper, the outage performance is investigated for orthogonal frequency division multiplexing (OFDM)-based selective amplify-and-forward cooperative networks over independent but not identically distributed (i.n.i.d.) Nakagami-m fading channels, with integer values of parameter m. A unified closed-form expression for the outage probability is derived for three selective relaying schemes. The...
We investigate the outage probability for amplify-and-forward (AF) and decode-and-forward (DF) relaying in OFDM-based cooperative networks. To minimize the outage probability, the relay which has the maximum received SNR is selected as the cooperative relay. Based on the relay selection, the problems of optimal power allocation and placing relays in the optimal position are discussed. And the expressions...
Frequency synchronization plays a critical role in acquiring cooperative diversity for cooperative OFDM systems. However, the superposition of different carrier frequency offsets (CFOs) among each relay and destination makes the estimation difficult. In this paper, a novel multiple CFOs estimation algorithm is proposed. With this algorithm, the CFO corresponding to each relay can be accurately estimated...
IEEE 802.16j is to enable the operation of multi-hop Relay Stations (RS). It aims to enhance the coverage, per user throughput and system capacity of IEEE 802.16e. However, the Mobile Stations (MSs) which connect to the RS are suffering from exponentially throughput degradation and end-to-end delay increase in congested network. As the number of RS hops increases, so does the degradation and the delay...
We consider a relay-assisted wireless communication system where relays are given the capability of scheduling function. We evaluate and compare the performances of voice over internet protocol (VoIP) in orthogonal frequency division multiple access (OFDMA) systems where two different scheduling capabilities of relays are employed in each system. In the system with relays that have the scheduling...
In this paper, we consider the optimal resource allocation problem for dual-hop systems with a source-destination pair and multiple decode-and-forward (DF) relays. Orthogonal frequency division multiplexing (OFDM) is adopted in both hops. To maximize the system capacity, we formulate a mixed binary integer programming problem to optimally allocate the subchannels and transmit power for both the source...
We propose a dynamic resource allocation scheme for a wireless cooperative network based on orthogonal frequency division multiplexing (OFDM) modulations with limited feedback. The amount of the feedback information required from the relay to the source in the proposed scheme is independent of the number of subchannels, which results in a dramatic reduced overhead over conventional resource allocation...
In cooperation relay system, two relay stations transmit cooperatively for the relay link users, and the relay link users receive signal by maximal ratio combining. The traditional multiuser scheduling algorithms, Max C/I algorithm for system throughput maximization and proportional fairness (PF) algorithm for user fairness, are extended into the DF cooperative relay systems. The simulation results...
Selective relaying periodically selects one single relay with the best channel quality to participate the communication between source and destination. When OFDM is used as the physical layer technique in the network, a new problem is how to select the best relay since independent subcarriers may have different channel conditions. Several schemes have been presented, while their capacities are still...
An adaptive power allocation algorithm called two-hop power allocation (THPA) is proposed to guarantee two-hop data rate balance in regenerative OFDM relay systems. The aim of this algorithm is power efficiency at the transmission node. The base station (BS) or relay station (RS) adjust power adaptively in terms of the difference between the first hop link data rate and the second hop link data rate...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.