Realtime Multi-User Multi-Antenna Downlink Measurements

2013 IEEE International Conference on Communications Workshops (ICC)

et al. 2013

In this paper, we investigate an efficient MAC protocol for interference coordination in small cells embedded in a macro-cell mobile network. We perform joint transmission (JT)-coordinated multi-point (CoMP), where cells in the cluster include adjacent macro-cells as suggested by the small-cell terminal. Most gains compared to uncoordinated transmission come from selecting the right users in these macro-cells. For minimizing the feedback overhead, we propose successive channel state information (CSI) requests. Thereby we replace users in the set until all of them experience consistently enhanced performance when using JT-CoMP. Gains can be further increased by MIMO mode switching in each cell and frequency-selective scheduling. We tested our algorithms over coherently measured multi-cell channels in the LTE-Advanced testbed in Berlin where small cells were embedded at several places. Using these algorithms, performance becomes comparable to a popular bound assuming no more intra-cluster interference while feedback overhead and complexity are substantially reduced

Section: ) Successive Feedback Requestsmentioning

confidence: 99%

“…Nt t=1 0.9 · log 2 (1 + 0.85 · σ t,n,i ) − 0.18 (11) where N is the number of subcarriers, N t the number of transmit antennas and i the channel realization.…”

Section: B Evm-based Sinr Estimationmentioning

confidence: 99%

Efficient MAC protocol for JT CoMP in small cells

Lossow

Jaeckel

2013 IEEE International Conference on Communications Workshops (ICC)

et al. 2013

“…[8] for an initial implementation example. In the MAC processor, packets are classified according to the internet protocol (IP) packet number, destination address and type of service (TOS) fields extracted from the IP header [18].…”

Section: Mac Layer Synchronizationmentioning

confidence: 99%

“…3G Long Term Evolution (3G-LTE). A cellular trial system with 2 transmit and 2 receive antennas in 20 MHz bandwidth has been implemented [7] and tested [8]. Although the basic MIMO technology is quite similar, the numbers of in-and outputs for cooperative base stations and hence the complexity are further increased.…”

Section: Introductionmentioning

confidence: 99%

Synchronization of cooperative base stations

2008 IEEE International Symposium on Wireless Communication Systems

Wirth

Schellmann

et al. 2008

Self Cite

Abstract-We consider synchronization techniques required to enhance the cellular network capacity using base station cooperation. In the physical layer, local oscillators are disciplined by the global positioning system (GPS) and over the backbone network for outdoor and indoor base stations, respectively. In the medium access control (MAC) layer, the data flow can be synchronized by two approaches. The first approach uses so-called time stamps. The data flow through the user plane and through copies of it in each cooperative base station is synchronized using a timing protocol on the interconnects between the base stations. The second approach adds mapping information to the data after the user plane processing is almost finalized. Each forward-error encoded transport block, its modulation and coding scheme and the resources where it will be transmitted are multicast over the interconnect network. Interconnect latency is reduced below 1 ms to enable coherent interference reduction for mobile radio channels.

“…We have implemented the distributed CoMP concept in real time on top of an existing LTE trial system described previously [19][20][21]. Implementation of enabling features such as clock synchronization, synchronous data exchange, cell specific pilots, CSI feedback, cooperative precoding, precoded pilots and initial laboratory trials are reported in [22].…”

Section: Introductionmentioning

confidence: 99%

Field trials using coordinated multi-point transmission in the downlink

2010 IEEE 21st International Symposium on Personal, Indoor and Mobile Radio Communications Workshops

Forck

Jaeckel

et al. 2010

Self Cite

Abstract-We report on field trials using CoMP transmission in the downlink of a mobile radio network. Two new features enable over-the-air CoMP transmission from physically separated base stations and terminals. These are distributed synchronization and a fast virtual local area network. Using VLAN tags, terminals feed back the multi-cell channel state information to their serving bases where it is multiplexed with shared data. Both are multicast to other cooperative base stations over the backhaul. In our trials, two terminals are served in two overlapping cells and placed in specific indoor, outdoor-to-indoor and outdoor scenarios. We have realized both intra-site as well as inter-site CoMP. While outage is indeed a big problem at the cell edge with full frequency reuse, with CoMP it is not observed anymore. Average throughput gains by factors 4 to 22 are observed when using CoMP compared to interference-limited transmission while between 27 and 78% of the isolated cell throughput is measured in both cells simultaneously.