| 1. |
- Seifi, Nima, 1981-, et al.
(författare)
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An Efficient Signaling for Multi-mode Transmission in Multi-user MIMO
- 2010
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Ingår i: IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP'10), Dallas, USA, Mar. 2010.. - 1520-6149. - 978-142444296-6 ; s. 3402-3405
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Konferensbidrag (refereegranskat)abstract
- In this paper the downlink of a multi-user MIMO (MUMIMO) system with multi-mode transmission is considered. We propose a low-complexity algorithm for selecting users and the corresponding number of data streams to each user, denoted as user transmission mode (UTM). The selection is only based on the average received signal-to-noise ratio (SNR) from the base station (BS) for each user. This reduces the overall amount of feedback for scheduling, as opposed to techniques that assume perfect instantaneous channel state information (CSI) from all users. Analytical average throughput approximations are derived for each user at different UTMs. Simulation results demonstrate that the proposed algorithm provides performance close to dirty paper coding (DPC) with considerably reduced feedback.
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| 2. |
- Seifi, Nima, 1981-, et al.
(författare)
-
Coordinated Single-Cell vs Multi-Cell Transmission with Limited-Capacity Backhaul
- 2010
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Ingår i: IEEE Asilomar Conf. on Signals, Systems, and Computers, Pacific Grove, CA, Nov. 2010.
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Konferensbidrag (refereegranskat)abstract
- Base station coordination is an efficient technique to transcend the limits on spectral efficiency imposed by intercell interference. In this paper, we compare the performance of different coordination strategies with different amount of channel state information (CSI) and data sharing among the coordinating base stations. We focus on the effect of limited backhaul capacity in a two-cell network. Contrary to the common belief, we show that coordination strategies with no data and only limited CSI sharing is preferred to those with full data and CSI sharing when the backhaul capacity is relatively low and the edge SNR is high.
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| 3. |
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| 4. |
- Seifi, Nima, 1981-, et al.
(författare)
-
Impact of base station antenna tilt on the performance of network MIMO systems
- 2012
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Ingår i: IEEE 75th Vehicular Technology Conference, VTC Spring 2012, Yokohama, 6 May-9 June 2012. - 1550-2252. - 978-146730990-5
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Konferensbidrag (refereegranskat)abstract
- We study the downlink of a multicell MIMO system where clusters of multi-antenna base stations jointly serve multiple single-antenna users, commonly referred to as a network MIMO system. Most of the previous studies on network MIMO have only considered the azimuth pattern of the antenna, while ignoring the elevation pattern. In this paper, we consider both the azimuth and the elevation patterns and investigate the impact of the elevation angle tuning parameter, denoted as the antenna tilt, on the performance of such systems. Using system simulations, it is shown that the promised performance gains of network MIMO systems over conventional non-coordinated systems, crucially depend on the choice of the right tilt setting including the tilt type, i.e., mechanical or electrical, and the tilt angle. In particular, for tilt angles smaller than the optimum, network MIMO with intra-site coordination performs almost as well as the conventional system; while for tilt angles larger than the optimum, the performance of network MIMO with intra-site is similar to that of network MIMO with inter-site coordination.
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| 5. |
- Seifi, Nima, 1981-, et al.
(författare)
-
Multimode Transmission in Network MIMO Downlink with Incomplete CSI
- 2011
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Ingår i: EURASIP Journal on Advances in Signal Processing, special issue on Cooperative MIMO Multicell Networks, 2011. - 1687-6172.
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Tidskriftsartikel (refereegranskat)abstract
- We consider a cooperative multi-cell MIMO (a.k.a network MIMO) downlink system with multiantenna base stations (BSs), which are connected to a central unit and communicate with multi-antenna users. In such a network, obtaining perfect channel state information (CSI) of all users at the central unit to exploit opportunistic scheduling requires a substantial amount of feedback and backhaul signaling. In this paper, we propose a scheduling algorithm based only on the knowledge of the average received SNR at each user from all the cooperating BSs, denoted as incomplete CSI. Multi-mode transmission is applied that is able to adaptively adjust the number of data streams transmitted to each user. Utilizing the results of random matrix theory, an analytical framework is proposed to approximate the ergodic rate of each user with different number of data streams. Using these approximate ergodic rates, a joint user and mode selection algorithm is proposed, where only the scheduled users need to feed back instantaneous CSI. Simulation results demonstrate that the developed analytical framework provides a good approximation for a practical number of antennas. While substantially reducing the feedback overhead, it is shown that the proposed scheduling algorithm performs closely to the opportunistic scheduling algorithm that requires instantaneous CSI feedback from all users.
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| 6. |
- Seifi, Nima, 1981-, et al.
(författare)
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Simulation of a wideband reconfigurable multi-antenna system with space-time coding
- 2008
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Ingår i: Nordic Matlab Users Conference, Stocholm, Sweden, November 2008.
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Konferensbidrag (refereegranskat)abstract
- Multiple-Input Multiple-Output (MIMO) systems will play a crucial role in the future of wireless systems, for example multiple antenna techniques can be a key to boost the performance of modern wireless systems. In order to study the performance and complexity of MIMO systems, a suitable simulation tool is essential. Simulation is important in system architecture exploration, algorithm optimization and bottleneck detection. Simulation is also a powerful tool when designing various components in an antenna system like electromagnetic solvers for radiation patterns and circuit simulation for amplifiers, but simulating an entire antenna system is not usual. In this paper the capabilities of MathWorks Simulink as a simulation platform for MIMO systems have been investigated and a typical MIMO-WCDMA link has been developed. Some of the blocks were used from the WCDMA library and others were developed accordingly. The Space-Time encoder and decoder for a general MIMO link were also developed. Furthermore, in order to be able to test different antenna types in a system, the antenna block is separated from the channel. Henceforth a double directional channel has been developed based on the SCM (spatial channel model) proposed by 3GPP (3rd Generation Partnership Project), which is an environmental channel independent from the antenna. The results of the simulation shows that Simulink is a capable platform for simulation of an entire communication link.
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| 7. |
- Seifi, Nima, 1981-, et al.
(författare)
-
Throughput Optimization for MISO Interference Channels via Coordinated User-Specific Tilting
- 2012
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Ingår i: IEEE Communications Letters. - 1089-7798. ; 16:8, s. 1248-1251
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we propose a novel framework to enhance the throughput in multiple-input single-output (MISO) mutually interfering channels via selecting the tilt angles at all base stations (BSs) in a coordinated fashion. In the proposed framework, multiple BSs adjust their tilt angles jointly to maximize the sum throughput of the scheduled users, denoted as coordinated user-specific tilting. Assuming the availability of location information of the scheduled users at all BSs, accurate analytical expression for user ergodic rate is provided, which enables a decentralized deployment of the proposed framework at each BS. Simulation results show that the proposed coordinated user-specific tilting scheme outperforms the conventional schemes employing a fixed tilt angle at each BS.
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