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  • 101.
    Shalmashi, Serveh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Slimane, Ben
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Interference management for multiple device-to-device communications underlaying cellular networks2013Ingår i: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE conference proceedings, 2013, s. 223-227Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the problem of interference management for device-to-device (D2D) communications where multiple D2D users may coexist with one cellular user. The problem is to optimize the transmit power levels of D2D users to maximize the cell throughput while preserving the signal-to-noise-plus-interference ratio (SINR) performance for the cellular user. This is the so-called multi rate power control problem. We investigate the problem under two assumptions, the availability of the instantaneous or average channel state information (CSI) at the base station. In the first case, D2D transmit power levels adapt to fast fading, whereas in the second case, they only adapt to slow fading. In the latter assumption, the cellular user has a maximum outage probability requirement. With numerical results, we study the trade-off between the signaling overhead, that is frequent CSI feedbacks, and the overall system performance, that is the maximum achievable cell capacity, for D2D communications underlying cellular networks.

  • 102.
    Shalmashi, Serveh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Slimane, Ben
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Cooperative Device-to-Device Communications in the Downlink of Cellular Networks2014Ingår i: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), 2014, s. 2265-2270Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose a cooperative device-to-device (D2D) communications framework in order to combat the problem of congestion in crowded communication environments. The idea is to allow a D2D transmitter to act as an in-band relay for a cellular link and at the same time transmit its own data by employing superposition coding in the downlink. Cooperation between the cellular link and D2D transmitter eases down the requirement on the interference. The main benefit of the proposed method is in increasing the number of connections per unit area with the same spectrum usage. It could also be beneficial to offload over-loaded cells. We formulate our problem to minimize the assigned power for cooperation while making sure the cellular user’s performance does not degrade. Our results show that cooperation possibilities and improvement in overall cell capacity increase with the number of cellular users within the cell as well as the cell size.

  • 103.
    Shalmashi, Serveh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Slimane, Ben
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    On Secondary User Transmission Schemes in Relay-Assisted Cognitive Radio Networks2013Ingår i: 2013 IEEE 77th Vehicular Technology Conference (VTC Spring), IEEE , 2013, s. 6692665-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a cooperative cognitive radio network with one primary user and many secondary users. In each transmission frame, one secondary user is selected to act as a relay for the primary user and also transmits its own data. Three different schemes for the secondary user's transmission is studied, namely, time-splitting, superposition coding, and a combined scheme that takes advantages of both time-splitting and superposition coding schemes. We formulate the relay selection problem for each scheme with the objective of maximizing the secondary user's data rate while satisfying a pre-defined gain threshold for the primary user. This constraint provides an incentive for the primary user when allowing the secondary user access its licensed band. We obtain the optimal solution for this problem in each scheme, on which the relay selection is based on. Finally, we compare the performance of different schemes using Monte-Carlo simulations.

  • 104.
    Shalmashi, Serveh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Slimane, Ben
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Performance analysis of relay-assisted cognitive radio systems with superposition coding2012Ingår i: Proceedings of the IEEE 23rd International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE , 2012, s. 1226-1231Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the problem of relay selection in a cooperative cognitive radio system in which a secondary transmitter can act as a relay for the primary transmitter in order to maximize the primary user's gain. Moreover, we take into account that the secondary users may have certain quality-of-service (QoS) requirements which need to be satisfied. In the cooperative scenario of a cognitive radio system, the primary user should have an incentive to allow the secondary user to transmit in its licensed band. At the same time, the secondary user should be able to transmit its own data with the required QoS in order to be willing to help the primary user's performance by relaying its data. Hence, we take into account both primary and secondary users' objectives. We use numerical methods in order to study how different parameters, such as assigned powers in the coding scheme, direct link reliability, and the number of secondary users affect the overall system performance. Our results show that the gain, which the primary user can achieve by cooperation, highly depends on the quality of its direct link as well as the secondary users' QoS requirements. Furthermore, the percentage of cooperation instances between secondary users and the primary user is dependent on the amount of power the secondary users allocate for relaying the primary's signal based on the direct link quality.

  • 105.
    Singh, Vaibhav
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Yilmaz, Oya
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Reddy, Karthigeyan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    On the Downlink Capacity of WCDMA Systems with Transmit Diversity2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Transmitter diversity at the base station has been included in WCDMA standard for third generation mobile systems as a means of increasing the downlink system capacity. In previous works, it has been shown that open loop transmitter diversity can significantly increase the downlink capacity. However, the performance in multipath environment is not known. In our study, we present the simulation results for downlink system capacity taking into account the effect of Doppler frequency and multipath fading. The results show that even in severe multipath wireless channel, diversity scheme can greatly improve the system capacity when no soft handover is used.

  • 106.
    Timus, Bogdan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Performance analysis of an amplify and forward relaying scheme with pre-coding2007Ingår i: 2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9, IEEE , 2007, s. 2834-2838Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cooperative diversity can combat fading on multipath channels by exploiting space diversity available through cooperative relays. Half-duplex relaying is quite simple to implement but it is useful only when the direct link is weak. By allowing the source to transmit continuously, full-rate relay channels can be obtained. However, the performance of such a full-rate scheme is still limited by the direct link. In this paper1 we consider pre-coding at the transmitter as a way of improving the performance of full-rate relay channels. The obtained results show that, with a proper selection of the pre-coding parameters, better system capacity can be obtained.

  • 107.
    ur Rehman Ahsin, Tafzeel
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A Joint Channel-Network Coding Based on Product Codes for the Multiple-Access Relay Channel2012Ingår i: ISRN Communications and Networking, ISSN 2090-4355, E-ISSN 2090-4363, Vol. 2012, s. 1-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The multiple access relay channel with network coding has the potential to achieve diversity and improve coverage of wireless networks. Its network coding scheme provides an extra redundancy that can be used at the receiver to improve the performance of the cooperating users. This paper shows that the combination of channel coding and network coding, in the multiple access relay channel, can be seen as a product code with rows formed by the code-words of the individual channel codes of the users and columns formed by the network coding code-words. This new representation allows the use of any decoding algorithm of product codes at the receiver to decode the information data of the cooperating users. This decoding process is a complete joint channel-network decoding algorithm as it sees the combination of the two coding schemes as a single coding scheme. It also gives the possibility to use network coding schemes more powerful than conventional XOR-based network coding. The obtained results show that the proposed product-based network coding structure can improve the performance of themultiple-access relay channel without reducing its efficiency and allow a very flexible cooperation between the involved users.

  • 108.
    ur Rehman Ahsin, Tafzeel
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Area energy consumption in cooperative decode and forward (DF) relaying scenarios2011Ingår i: European Wireless 2011, 2011, s. 393-400Konferensbidrag (Refereegranskat)
    Abstract [en]

    Energy efficiency in cellular networks has become an important design parameter in recent research works due to the global climate change and growing demand for very high data rates in future cellular systems. In our work, the main objective is to reduce the area energy consumption in a cellular network, for a given average spectral efficiency, in order to realize the green radio transmissions. The energy consumption for different transmission schemes such as direct link, decode and forward (DF) relaying with and without network coding is compared in this regard using a linear power consumption model. The impact of different parameters such as cell radius, the number and position of deployed relays and target spectral efficiency is studied for each transmission scheme. It has been concluded that DF relaying in general, provides moderate power savings as compared to the direct link transmission. Moreover, for a given outage probability, the network coding at the relay extends the cell coverage and provides higher spectral efficiency as compared to the conventional DF relaying and the direct transmission.

  • 109.
    Xu, Jie
    et al.
    University of Science and Technology of China.
    Qiu, Ling
    University of Science and Technology of China.
    ur Rehman Ahsin, Tafzeel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Scheduling, Pairing and Ordering in the Network Coded Uplink Multiuser MIMO Relay Channels2010Ingår i: 2010 IEEE 71ST VEHICULAR TECHNOLOGY CONFERENCE, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Network coded multiuser uplink MIMO channels have been discussed in this paper. A three slots transmission is considered here and spatial division multiple access (SDMA) has been employed to serve multiuser simultaneously. Minimum mean-square-error successive interference cancellation (MMSE-SIC) is applied in the first two slots and singular value decomposition (SVD) is applied for the third slots. In order to get the optimal performance, user scheduling, decoding ordering and user pairing need to be considered. However, the optimal exhaust searching algorithm is too complex to implement. We propose a low complexity scheme to solve this problem and the simulation results show the performance gain. The proposed scheme is promising in the real systems.

  • 110. Zafar, B.
    et al.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Javed, Muhammad Umar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Network product coding2010Ingår i: 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010, IEEE , 2010, s. -266Konferensbidrag (Refereegranskat)
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users. Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code. We seek to employ product coding can be able to support more than two users/packets per relay per slot, while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network.Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

123 101 - 110 av 110
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