PHY Layer NCHU CSE WMAN - 1

Transcription

1 PHY Layer NCHU CSE WMAN - 1

2 Multiple Access and Duplexing Time-Division Duplex (TDD) DL & UL time-share the same RF channel Dynamic asymmetry (also named as Demand Assigned Multiple Access : DAMA) Half-duplex SS does not transmit/receive simultaneously (low cost) Frequency-Division Duplex (FDD) DL & UL on separate RF channels Static asymmetry Full-duplex SSs supported Half-duplex SSs supported (low cost)» SS does not transmit/receive simultaneously» Need resynchronization NCHU CSE WMAN - 2

3 TDD Frame Frame duration: 0.5/1/2 ms (SC), 2.5/4/5/8/10/12.5/20 ms (OFDM), 2/2.5/5/8/10/12.5/20ms (OFDMA) Physical Slot (PS) = 4 symbols (SC/a), 4/sampling_freq(Fs) (OFDM/A) Minislot : A unit of uplink bandwidth allocation equivalent to n physical slots (PSs), where n = 2 m and m is an integer ranging from 0 through 7. NCHU CSE WMAN - 3

4 Adaptive Burst Profiles Burst profile Modulations and FEC AMC : Advanced Modulation and Coding Dynamically assigned according to link conditions Burst by burst, per subscriber station Trade-off capacity vs. robustness in real time Roughly doubled capacity for the same cell Burst profile for downlink channel (broadcast) is wellknown and robust Other burst profiles can be configured on the fly SS capabilities recognized at registration» SBC-REQ/RSP SS Basic Capability Request NCHU CSE WMAN - 4

5 System Parameters QPSK, 16-QAM and 64-QAM NCHU CSE WMAN - 5

6 Radio Link control (RLC) RLC control transition of burst profile power level ranging RLC begins with periodic BS broadcast of the burst profiles that have been chosen for the uplink and downlink according to rain region and equipment capabilities. Burst profiles for the downlink/uplink are each tagged with a Downlink/Uplink Interval Usage Code (DIUC/UIUC). NCHU CSE WMAN - 6

7 Burst Profile Burst profile is a basic tool for MAC to do link adaptation Containing a set of PHY-related parameters which changes dynamically and possibly very fast Set of parameters that describe the uplink or downlink transmission properties associated with an interval usage code (IUC). The burst profile to use for any uplink transmission is defined by the Uplink Interval Usage Code (UIUC). Each UIUC is mapped to a burst profile in the UCD message Each profile contains parameters such as a) modulation type b) forward error correction (FEC) type c) preamble length d) guard times NCHU CSE WMAN - 7

8 Burst Profile If the received CINR (Carrier to Interference-plus- Noise Ratio) goes outside of the allowed operating region, the SS requests a change to a new burst profile using one of two methods 1. If the SS has been granted uplink bandwidth, it shall send a DBPC-REQ message in that allocation. The BS responds with a DBPC-RSP message. 2. If grant is not available and the SS requires a more robust burst profile on the downlink, it shall send a RNG-REQ message in an Initial Ranging interval. Note : using the Basic CID of the SS Downlink Burst Profile Change Request (DBPC-REQ) NCHU CSE WMAN - 8

9 Uplink Channel Descriptor (UCD) message Configuration Change Count Incremented by one (modulo 256) by the BS whenever any of the values of this channel descriptor change. This value is also referenced from the UL-MAP messages. UCD Count Matches the value of the Configuration Change Count of the UCD, which describes the uplink burst profiles that apply to this map. The Uplink_Burst_Profile is a compound TLV encoding that associates with a UIUC, NCHU CSE WMAN - 9

10 Burst Profile Transition As SS receives unclear signals! C/(N+I) :carrier to noise and interference ratio DL-MAP RNG-REQ or DBPC-REQ change to DIUC k DL Data more or equally robust as DIUC k RNG-RSP or DBPC-RSP (at DIUC k) Continue monitor DL data on DIUC more or equally robust as DIUC n Ranging request (RNG-REQ) or downlink burst profile change request (DBPC-REQ) (page 8) Continue monitor DL Data on DIUC more or equally robust as DIUC k DL Data more or equally robust as DIUC k Transition to a more robust operational burst profile. NCHU CSE WMAN - 10

11 Burst Profile Transition As SS receives strong signals! DL Data more or equally Robust as DIUC n C/(N+I) :carrier to noise and interference ratio DBPC-REQ change tp DIUC m Start monitor DL data on DIUC more or equally robust as DIUC m DBPC-RSP (at DIUC m ) DL Data more or equally Robust as DIUC m Transition to a less robust operational burst profile. NCHU CSE WMAN - 11

12 Burst Profile Threshold C/(N+I) :carrier to noise and interference ratio NCHU CSE WMAN - 12

13 Map Relevance and Synchronization (TDD) ATDD : adaptive time division duplexing NCHU CSE WMAN - 13

14 Map Relevance and Synchronization (FDD) NCHU CSE WMAN - 14

15 Map Relevance WirelessMAN-SC PHY & WirelessMAN-OFDM PHY Allocation Start Time (AST) is subject to the following limitations:» FDD : minimum AST value = round trip delay + T proc, maximum AST value = T f (i.e., the beginning of the next frame).» TDD : the AST value is either the ATDD split or the ATDD split + T f. The allocation shall be within a single frame. WirelessMAN-SCa PHY & WirelessMAN-OFDMA PHY Allocation Start Time shall be subject to the following limitations:» Minimum value: Allocation Start Time T f» Maximum value: Allocation Start Time < 2 T f NCHU CSE WMAN - 15

16 Adaptive Antenna System A system adaptively exploiting more than one antenna to improve the coverage and the system capacity Adapt the antenna pattern and concentrating its radiation to each individual subscriber The spectral efficiency can be increased linearly with the number of antenna elements steering beams to multiple users simultaneously so as to realize an inter-cell frequency reuse NCHU CSE WMAN - 16

17 Adaptive PHY Adaptive modulation NCHU CSE WMAN - 17

18 Optional MAC AAS Support Support in WirelessMAN-SCa, OFDM, and OFDMA signal-to-noise ratio (SNR) gain realized by coherently combining multiple signals, and the ability to direct this gain to particular users. Reduce interference MIMO/SIMO/MISO. NCHU CSE WMAN - 18

19 Optional MAC AAS Support Provides a mechanism to migrate from a non-aas system to an AAS enabled system dedicating part of the frame to non-aas traffic and part to AAS traffic time NCHU CSE WMAN - 19

20 Optional MAC AAS Support Alerting the BS about presence of a new SS in an AAS system AAS BS may reserve a fixed, pre-defined part of the frame as initial-ranging contention slots (called AAS-alert-slots) for this alert procedure FDD/TDD support use channel state information of both downlink and uplink Two ways :» (reciprocity) using the uplink channel state estimation as the downlink channel state (TDD)» (feedback) transmitting the estimated channel state from the SS to BS. (FDD or TDD) using two MAC control messages:» AAS-FBCK-REQ and AAS-FBCK-RSP» The BS shall provide an uplink allocation to enable the SS to transmit this response.» Using FDD, the BS shall issue AAS-FBCK-REQ messages.» Using TDD, the BS may issue AAS-FBCK messages. (pp. 165) NCHU CSE WMAN - 20

21 Scheduling Flexibility Allows scheduling flexibility NCHU CSE WMAN - 21

22 Uplink TDD/FDD Subframe (ranging) (band. req) UIUC: Uplink Interval Usage Code NCHU CSE WMAN - 22

23 TDD Downlink Subframe Well known DIUC: Downlink Interval Usage Code NCHU CSE WMAN - 23

24 Receive/transmit Transition Gap (RTG) in TDD A gap between the uplink burst and the subsequent downlink burst in a TDD transceiver. Not applicable for FDD systems transmit/receive transition gap (TTG) : similar NCHU CSE WMAN - 24

25 FDD Downlink Subframe Well known TDMA portion: transmits data to some half-duplex SSs (the ones scheduled to transmit earlier in the frame than they receive) Need preamble to re-sync (carrier phase) NCHU CSE WMAN - 25

26 Nine Data Rates in Modulation Schemes : QPSK, 16-QAM and 64-QAM 20 MHz/channel (4M PSs/frame/ms = 16Msymols/ms) 32Mbps / 64Mbps / 96Mbps 25 MHz/channel (5M PSs/frame/ms = 20Msymbols/ms) 40Mbps / 80Mbps / 120Mbps 28 MHz/channel (5.6M PSs/frame/ms = 22.4Msymbols/ms) 44.8Mbps / 89.6Mbps / 134.4Mbps Uplink mandatory US European downlink mandatory 0.5, 1 or 2 ms NCHU CSE WMAN - 26

27 Data Rate in e OFDMA NCHU CSE WMAN - 27

28 10-66 GHz PHY parameters NCHU CSE WMAN - 28

29 Uplink PHY NCHU CSE WMAN - 29

30 Downlink PHY NCHU CSE WMAN - 30

31 Shortened FEC blocks TDMA/TDM case Reed-Solomon over Galois field GF(256) TDMA w/ TDM w/o NCHU CSE WMAN - 31

32 IEEE a Medium Access Control Modifications and Additional Physical Layer Specifications for 2-11 GHz NCHU CSE WMAN - 32

33 802.16a PHY Alternatives Different Applications, Bandplans, and Regulatory OFDM (WirelessMAN-OFDM Air Interface) 256-point FFT with OFDM (TDD/FDD) OFDMA (WirelessMAN-OFDMA Air Interface) 2048-point FFT with OFDMA (TDD/FDD) CDMA ranging code Single-Carrier (WirelessMAN-SCa Air Interface) TDMA (TDD/FDD) BPSK, QPSK, 4-QAM, 16-QAM, 64-QAM Most vendors will use Frequency-Domain Equalization for solving delay spread issue NCHU CSE WMAN - 33

34 Key a MAC/PHY Features 2-11GHz License-exempt band 5-6 GHz OFDM/OFDMA support ARQ Space-Time Coding (STC) There are two transmit antennas on the BS side and one reception antenna on the SS side. Dynamic Frequency Selection (DFS) license-exempt Adaptive Antenna System (AAS) support Mesh Mode Optional topology for license-exempt operation only (TDD only) Subscriber-to-Subscriber communications (Mesh mode) Complex topology and messaging NCHU CSE WMAN - 34

35 Features OFDM (WirelessMAN-OFDM Air Interface) Two contention based BW request mechanisms 1. Bandwidth Request Header 2. Focused Contention Transmission with Contention Code over Contention Channel consisting of 4 carriers OFDMA (WirelessMAN-OFDMA Air Interface) Two contention based BW request mechanisms 1. Bandwidth Request Header 2. Specifies a Ranging Subchannel and a subset of Ranging Codes that are used for contention-based BW requests (CDMA mechanism) The WirelessHUMAN system provides optional support for Mesh topology. Unlike the point-2-multipoint (PMP) mode, there are no clearly separate downlink and uplink subframes in the Mesh mode. HUMAN : High-Speed Unlicensed Metropolitan Area Network NCHU CSE WMAN - 35

36 Mesh-based WirelessMAN Roofnet?? Source: Nokia Networks NCHU CSE WMAN - 36

37 WirelessHUMAN Mesh deployment model NCHU CSE WMAN - 37

38 Mesh Networks Mesh systems typically use omnidirectional or 360 steerable antennas, but can also be co-located using sector antennas. Directed Mesh (DM) : The realization of a physical mesh using substantially directional antennas. Nodes : systems in Mesh networks Mesh BS : a system that has a direct connection to backhaul services outside the Mesh network. Mesh SS : all the other systems of a Mesh network Neighbor : The nodes with which a node has direct links Neighborhood :Neighbors of a node form a neighborhood (one-hop) Extended neighborhood : all the neighbors of the neighborhood (two-hops) NCHU CSE WMAN - 38

39 Mesh Networks Using distributed scheduling, all the nodes including the Mesh BS shall coordinate their transmissions in their two-hop neighborhood and shall broadcast their schedules (available resources, requests and grants) to all their neighbors. The schedule may also be established by directed uncoordinated requests and grants between two nodes. (Optionally) Nodes shall ensure that the transmissions do not collide with the traffic scheduled by any other node in two-hop neighborhood. Both the coordinated and uncoordinated scheduling employ a three-way handshake Request/Grant/Confirm NCHU CSE WMAN - 39

40 Mesh Networks Using centralized scheduling, the Mesh BS shall gather resource requests from all the Mesh SSs within a certain hop range. Ensure collision-free scheduling over the links in the routing tree Determine the amount of granted resources for each link each node shall compute it by using the predetermined algorithm with given parameters. QoS is provisioned over links on a message-by-message basis. NCHU CSE WMAN - 40

41 Mesh Networks 48-bit universal MAC address When authorized to the network the node receives a 16-bit node identifier (Node ID) upon a request to the Mesh BS Node ID is transferred in the Mesh subheader, which follows the generic MAC header, in both unicast and broadcast messages. For addressing nodes in the local neighborhood, 8-bit link identifiers (Link IDs) shall be used. The Link ID is transmitted as part of the CID in the generic MAC header in unicast messages. The Link IDs shall be used in distributed scheduling to identify resource requests and grants. Since these messages are broadcast, the receiver nodes can determine the schedule using the transmitter s Node ID in the Mesh subheader, and the Link ID in the payload of the MSH- DSCH (Mesh Mode Schedule with Distributed Scheduling) message. NCHU CSE WMAN - 41

42 Mesh Networks Link ID 8 bits Messages with larger Drop Precedence shall have higher dropping likelihood during congestion. NCHU CSE WMAN - 42

43 Mesh Networks Frame Structure NCHU CSE WMAN - 43

44 IEEE , 16a and 16e mobile Mesh topology * mobile HARQ mobile Mesh topology * 5-6GHz 5MHz/channel ; 200 channels HUMAN : High-Speed Unlicensed Metropolitan Area Network NCHU CSE WMAN - 44

45 Spectrum International Licensed ISM US Licensed International Japan Licensed Licensed UNII a has both licensed and license-exempt options License 2.3(Korea), 2.5(U.S.), 3.5(various countries), 4.8 GHz(Japan) License-exempt 2.4, 5.8 GHz (ISM) industrial, scientific and medical (ISM) Unlicensed National Information Infrastructure (U-NII) 5 6 GHz NCHU CSE WMAN - 45

46 Licensed Band Licensed Band: 2.5 GHz and 3.5 GHz License band has a more generous power budget Federal Communication Commission (FCC) has create the Broadband Radio Service (BRS) for wireless broadband access» GHz ~ GHz bands (US)» Question : what will happen if we design a gateway box with 2.4GHz b/g and 2.5GHz x NICs? European Telecommunications Standards Institute (ETSI) has allocated the 3.5 GHz band» Originally used for Wireless Local Loop (WLL) NCHU CSE WMAN - 46

47 Licensed-Exempt Band Licensed-Exempt Band: 5 GHz The majority usage around world is GHz and GHz Some governments and service providers concern the usage of the band could affect critical public and government communication networks» UK is currently introducing restriction on certain 5 GHz channels and enforcing the use of DFS function» Mexican government is moving toward licensing at least one of the 5 GHz to benefit the people Dynamic Frequency Selection NCHU CSE WMAN - 47

48 Spectrum Band and frequencies available for WiMAX Band Frequencies License Required Availability 2.5 GHz 2.5~2.69 GHz Yes Allocated in Brazil, Mexico, some Southeast Asian countries and U.S. Ownership varies by country 3.5 GHz 3.3~3.8 GHz (primary 3.4~3.6 GHz) Yes, in some countries In most countries, the 3.4 GHz to 3.6 GHz band is allocated for broadband wireless 5 GHz 5.25~5.85 GHz No In the GHz to 5.85 GHz portion, many countries allow higher power output (4W), which can improve coverage Source : Intel White Paper NCHU CSE WMAN - 48

49 Dynamic Frequency Selection DFS is mandatory for license-exempt operation A channel selection algorithm is required for uniform channel spreading across a minimum number of channels DFS procedures Testing channels for primary users» A BS or SS cannot use a channel which contains primary users Discontinuing operations after detecting primary users» If a BS or SS is operating in a channel and detects primary users Detecting primary users» Each BS and SS shall use a method to detect primary users in a channel Scheduling for channel testing» A BS may measure one or more channel itself and request SSs to measurement Requesting and reporting of measurements Selecting and advertising a new channel» A BS may decide to stop operating in a channel at any time NCHU CSE WMAN - 50

50 Mobility-WMAN Requirement (50mw) (0.5w) Adopted from : e requirements from an operator s perspective, Mar ant: antenna NCHU CSE WMAN - 51

51 Technical Glossary AAA Authentication Authorization Accounting BS Base Station BTC Block Turbo Code CMAC Cipher based Message Authentication Code CTC Convolutional Turbo Code DL Down Link Transmission (BS to MS) EAP Extensible Authentication Protocol FEC Forward Error Correction scheme FFT Fast Fourier Transform HMAC Hash based Message Authentication Code LE License Exempt LOS Line of Sight MAC Media Access Control (Logical Link Layer) MBS Multicast Broadcast Services NCHU CSE WMAN - 52

52 Technical Glossary MIB Management Information Base MIMO Multiple Input Mulitple Output (Multi Antenna transmissions) MS Mobile Station or Terminal N-LOS Non Line of Sight OFDM Orthogonal Frequency Division Multiplex OFDMA Orthogonal Frequency Division Multiple Access PKM Privacy Key Management Protocol PMK Pairwise Master Key QoS Quality of Service STC Space Time Coding TEK Traffic Encryption Key UL Up Link Transmission (MS to BS) NCHU CSE WMAN - 53

53 THANK YOU! Questions NCHU CSE WMAN - 54