Relay Based Deployments for Wireless & Mobile Systems

Transcription

1 Relay Based Deployments for Wireless & Mobile Systems Packet Relays: : a Disruptive Technology for Future Systems (Panel) Bernhard Walke ComNets, RWTH Aachen University EW 25, Nicosia, Cyprus Communication Networks

2 Deployment Studies Motivation Range of broadband base stations is limited, owing to high attenuation for high frequency carriers limited transmission power (EIRP limits) Unfavourable radio propagation conditions, e.g., in urban areas Increasing number of BS needed with increasing carrier frequency to cover a given area High CEX and OPEX High cost/bit transmitted hard to attract user In high capacity radio cell: High data rates available close to only With constant user density: Number of users at distance d increases with d Cell capacity offered per area element substantially differs from capacity requested by users Capacity/Area Element Actual Available Capacity vs. Requested Capacity Available Requested by users Distance d Cell border New Deployment Concepts required to bring broadband to wider area than possible with one base station in current systems Reduce the cost/bit transmitted by 2 to 3 orders of magnitude 2

3 Pros: Relays in REC don t need a wired backbone access (lowers CEX and OPEX) Full flexibility of relays (re-)positioning Relays introduced to cell can enlarge the coverage area Increase capacity at cell border balance the capacity/area element reduce transmission power increasing public acceptance Reducing co-channel interference (Movable) Relays support fast network rollout, outdoor to indoor service Exploitation of macrodiversity (co-operative relaying) Relay Enhanced Cells With Fixed Relay Stations (FRS) FRS Cons: In band relays consume radio resources Out of band relays need multiple transceivers Relays introduce extra delay 3

4 System Parameter Link Link Level Level Simulation Simulation results results for for HiperLAN/2 HiperLAN/2 OFDM OFDM Modem Modem [Ref.: [Ref.: Khun-Jush Khun-Jushet et al. al. VTC VTC Spring 99] Spring 99] 5 GHz GHz band band 2 2 dbm dbmtransmission power power dbm dbmnoise Perfect Perfect Link Link Adaptation Adaptation (LA) (LA) SREJ-ARQ SREJ-ARQ Throughput [Mbps] BPSK BPSK ½ BPSK BPSK ¾ QPSK QPSK ½ QPSK QPSK ¾ 16QAM 16QAM 9 / 9 16 / 16 16QAM 16QAM ¾ 64QAM 64QAM ¾ Max. Max. TP TP with with LA LA Throughput over SNR Analysis Analysis with with simple simple propagation propagation model: model: P R = P T * g T * g λ * 4π 1 * d P power power ;; g antenna antenna gain; gain; γγ- -pathloss pathlosscoefficient R 2 γ SNR [db] 4

5 L2-Relays are useful to bring coverage to shadowed areas End-to-End Throughput 1. Hop PHY Mode 1-2Hop PHY Mode 2-2Hop Throughput-Range gain from Relay FRS 2. Hop PHY-Mode 3-2Hop UT PHY Mode 4-2Hop PHY Mode 5-2Hop Distance Maximum End-2-End throughput over distance for 1- and 2-hop links with S-ARQ 5

6 2-Hop Cell in Manhattan Scenario 115 m FRS#1 Building Block Area covered by Fixed Relay Station (FRS) FRS#4 FRS#2 Area covered by Access Point () 23m FRS#3 3m Street Width 2m 2m 6

7 Different Deployment of Co-Channel Channel s Single-Hop Manhattan (a) UMTS 3.3 Placement (b) s at equal y-coords (c) s on street-crossings 7

8 Relay Enhanced Cell (REC) in Manhattan Scenario Cluster order N=2 Directly served by Fixed Relay Station (FRS) Served by FRS FRS serve to extend coverage of increase cell capacity FRS Building Block + 4 FRSs form a Relay Enhanced Cell 8

9 FRS sub-cell Capacity 25 capacity (Mbit/s) Mbit/s FRS sub-cell sub-cell Fixed Relay Station (FRS) FRS receive antenna gain (dbi) All capacity transferred to one FRS sub-cell Capacity of FRS rises until antenna gain allows using highest PHY mode without packet errors on first hop Relaying costs 6.67 Mbit/s of capacity at 3 dbi gain 9

10 Simulation Results vs. Analysis Two-Hop C/I and E-2-E E E Throughput: Manhattan End-to-End Throughput [Mbit/s] Throughput on Main Road +11,8dB Antenna Gain Distance [m] 2. Hop with 11,8dB antenna gain on 1st hop Analysis Shown Area 1 More detailed results in Esseling, N.; Walke, B. and Pabst, R.: Performance Evaluation of a Fixed Relay Concept for Next Generation Wireless Systems ; In Proceedings of PIMRC 24, p. 9, pp. 9, Barcelona, Spain, 9/24 End-to-End Throughput [Mbit/s] The results are based on MAC frame based system, e.g. WiMax/IEEE82.16e Throughput on Side Alley +11,8 db Antenna Gain on 1st Hop 2. Hop with 11,8dB antenna gain on 1st hop Distance [m] Analysis Shown Area 1

11 Wide Area Comparison Cases 2m 346m Area = FMT Antenna One-hop cell with R=346m is equivalent in coverage area to a two-hop cell with 3 FRSs, where each subcell has the radius R=2m 11

12 Deployment Scenario and Possible Frequency Plans Two-Hop Wide Area (a) Cluster Size N=3 (b) Cluster Size N=7 (c) Cluster Size N=12 12

13 Single Hop Cluster Size N=7 C/I in a Scenario with 1st Ring of co-channel interferers visible 6 4 Gleichkanalzelle Cell type: C/I [db] m Entfernung und MT (y) [m] Entfernung und MT (x) [m] End-zu-Ende-Durchsatz [Mbit/s] Max. End-to-End throughput in a celll Entfernung und MT (y) [m] Entfernung und MT (x) [m] 13

14 2-Hop Cluster Size dB Gbain Antennas FMT 6 FMT Cell type: 2m 4 2 C/I [db] -4 Entfernung und (R)MT (x) [m] Entfernung und (R)MT (y) [m] C/I over cell area FMT Antenna Ende-zu-Ende-Durchsatz [Mbit/s] -4 FMT FMT -4 Entfernung und (R)MT (x) [m] Max. End-to-End throughput in a cell Entfernung und (R)MT (y) [m] 14

15 2-Hop Cluster Size N=7 11.8dB gain Antennas on 1 st Hop 4 2 y Mbit/s 1Mbit/s 8Mbit/s x 6Mbit/s 4Mbit/s -2 2Mbit/s -4 15

16 Spectral Efficiencies 1 Manhattan Scenario Cell Capacity Scenario Used # of Cell Size Spect. Efficiency Freq. [m 2 ] / 1 3 [Mbit/s] [bit s -1 Hz -1 m -2 ] 1-Hop (s on cross.) 8 53,4 2,24 2,37 2-Hop N=2, +11,8dB 2 116, 1,72 2,31 Wide Area Scenario Cell Capacity Scenario Used # of Cell Size Spect. Efficiency Freq. [m 2 ] / 1 3 [Mbit/s] [bit s -1 Hz -1 m -2 ] 1-Hop Standard 346m ,53,35 2-Hop 3 FRS, +11,8 db ,44,4 In comparable deployments (s / Relays on crossings), the relaybased system offers the same spectral efficiency as the conventional system, with the advantage of considerably lower deployment efforts 2 1 R. Pabst, N. Esseling, B. Walke: Performance Evaluation of a Fixed Relay Concept for Next Generation Wireless Systems, EW25b 16

17 Cooperative Relaying Idea Direct Single-Path Relaying Cooperative Relaying Path gain: Interference or contribution? Single point-to-point link At layers 2, 3 Example: ODMA + Pathloss savings Need two phases + Exploits broadcast nature of wireless medium + Spatial diversity Additional path via relay Can emulate arrays virtual antenna arrays Point to point coding Network coding 17

18 Implementations of Relay based Deployments A: Homogeneous Relay -FRS (intra R) connection in Mode A R UT connection in Mode A B: Heterogeneous Relay -FRS (intra R) connection in Mode B R UT connection in Mode A Access Point Relay Station User Terminal Mode A Mode B Additional Mesh network to increase network resilience Cooperative Relaying 18

19 Conclusions Relays are a disruptive technology. Relay can Extend the coverage range of an Increase substantially the capacity of a cell Cover areas otherwise shadowed from the Reduce transmission power levels (when used to increase capacity) Relays & Smart Antennas offer opportunities to exploit spatial diversity Mesh networks may improve reliability 19