ROMANTIK. Management and AdvaNced. Transceiver AlgorIthms for Multihop NetworKs. Josep Vidal Universitat Politècnica de Catalunya (UPC)

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1 ROMANTIK ResOurce Management and AdvaNced Transceiver AlgorIthms for Multihop NetworKs Josep Vidal Universitat Politècnica de Catalunya (UPC)

2 Partners UPC Universitat Politècnica de Catalunya Prof. Josep Vidal Department of Signal Theory and Communications UoB University of Bristol Prof. Andrew Nix Centre for Communications Research DUN Dune, Ingegneria dei Sistemi Otello Gasparini INFO Università di Roma La Sapienza Prof. Sergio Barbarossa INFOCOM Department ICOM Intracom Anastasia Andritsou Development Projects Department FLE Fujitsu Laboratories of Europe Dr. Seshaiah Ponnekanti Advanced Radio Access Systems

3 General technical objectives Study structured and ad-hoc multi-hop radio networks Multilayer definition of multi-hop structures (based on TDD-UTRA, HIPERLAN/2) Develop strategies and algorithms - Multiple access technique for efficient MUD - Adaptive modulation (based on channel prediction) - Media Access Control (MAC) and Data Link Control (DLC) techniques - Radio Resource Management (RRM) tecniques - Routing algorithms Evaluate structured and ad-hoc multi-hop radio networks - Achievable capacity and range gains - Achievable power savings

4 Systems definition: Multihop TDD/UTRA (I) HBR coverage HBR-UE 3 LBR coverage 1 Sync info 2 LBR-UE HBR-UE No coverage 2 Feature 1: of Feature 2: 3: Coverage Interference extension reduction for users HSDPA. when outside every the user area may covered be by linked the infrastructure. through a relay connection even Infrastructure support: Infrastructure under coverage - Physical layer support: of the required BR. synchronism & slow - Infrastructure channel allocation support: of relay for last slots relay. - Synchronism Physical DL routing layer selected beyond synchronism by coverage RNC& slow area is channel provided allocation by last relay. of relay slots Scenario: - DL routing Scenario: Urban selected Urban black by black spots, RNC spots, rural. rural. Scenario: Urban Macrocells. Macrocells. black spots, rural. Macrocells.

5 Systems definition: Fixed relay for vertical handover HBR coverage LBR coverage LBR-UE No coverage Feature: Single hop for vertical handover UTRA-to-Hiperlan2. Access point WLAN picocell Infrastructure support: - Physical layer synchronism (in TDD) & slow channel allocation of relay slots. Sync info Scenario: HBR coverage of picocells, black spots.

6 Systems definition: Adhoc multihop for TDD/UTRA HBR coverage No coverage WLAN picocell Feature: Stand-alone TDD network with no infrastructure support, connection to AP. Infrastructure support: - No infrastructure support. Synchronism is propagated through the cell. Sync info Scenario: Picocells.

7 Interference reduction gain per route Interference reduction L/2 L/ Min reduction per phy. channel (tight reuse) Max reduction per phy. channel (loose reuse) L L/2 L/3 L/3 db Total interference reduction 1 hop 2 hops 3 hops 5 Propagation exponent α = 3.5 Interference reduction is proportional to α Number of hops Maximum reduction if all hops have the same length N physical channels are used per link

8 Power savings in structured relayed system (I) Relay unit Test Point

9 Power savings in structured relayed system (II)

10 The relay-relay communication in TDD TS0 TS1 TSi TS14 Restrictions in the symmetry: Minumum two time-slots for the relay-relay random access channel. Potentially any time-slot can be used by a dedicated channel (pre-determined in each cell). UL DL R-R

11 Intracell interference in TDD-based multihop Relay Relay R2 d i R1 At any position within the cell. If d i <78 m, delay diversity cannot be exploited (but MUD is affordable). Depends on the spatial distribution of traffic. Local minimisation of interference may increase interference globally (increase in other hops within a route).

12 Solutions for intracell interference reduction Distributed admission control Smart routing Power control (Relays) Distributed Dynamic Channel Allocation (DCA) (Relays) Limit the range in neighborhood search MU detection & interference cancelling Collision avoidance (for random access channels)

13 Physical layer: : CDMA-Cyclic Cyclic prefix extension Cyclic prefix extension of CDMA allows very simple MUD at the downlink (BS - relay). No cyclic prefix & full complexity rx RAKE No cyclic prefix & reduced complexity rx. Cyclic prefix MIMO architectures will be analysed with the goal of: Shortening the channel Increasing the spectral efficiency Decrease interference by array processing.

14 Physical layer: Adaptive modulation Find optimal waveforms to transmit information signals in time-frequency varying channels. Channel prediction is needed to determine in advance the optimum transmitted chirp signals. Multipath channel with 12 paths. The eigenvalue 1.25 of this channel has multiplicity 4 and the instantaneous frequencies are given by the red lines.

15 MAC layer: Random access protocols (I) Avoided by CS Not avoided by CS B A B A <> C C D B A C C A <> B D B and C are able to monitor the channel but they can not sense each other HIDDEN NODE PROBLEM B and C are not able to monitor the channel so they can not sense each other Efficiency of Carrier Sense (CS) contention-based protocols is decreased Reservation protocols avoid this problem but reservation procedure needs a random access channel! (contention problem in RTS/CTS is less important)

16 MAC layer: Random access protocols (II) CSMA without reservation Throughput with respect to: - Offered load - Packet size Results for spatial cancellation at the UL. High gains are observed with respect to single sensor reception. Throughput CSMA with reservation Offered load

17 Network layer: Routing protocols Both ad-hoc MHN and structured MHN, require QoS-preserving routing strategies coping with lower layers information like: 1. Channel state knowledge 2. Links congestion 3. Unstability of routes Routing repair Alternate routing Routing diversity

18 ROMANTIK Project duration: March 2002 to August