Contents: General about radio communications systems 3GPP WCDMA L1, the physical layer structure Transmitting and receiving Channels Codings Procedures Not included: Lauri Pirttiaho, NMP/Oulu diversity techniques, ARQ, power control, device classes etc. 1 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Radio communications system Physical radio link carries information from one system to another in a form of electromagnetic waves. The receiver is interfered by signals from other systems, and ever present physical noises. The Purpose of physical radio link is to establish a reasonably reliable radio communication path between the communicating system. In commercial systems some drivers for further development are: The capacity, or number of users serviced by the system. The data rate, or the qualities perceived by one user. 2 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
frequency Multiple Access Methods Multiple access refers to how different users access the system simultaneously. FDMA frequency time TDMA frequency Code time CDMA 3 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org time
Duplexing Methods Duplexing refers to how one user can establish a two way communications link with the system. frequency frequency time time Frequency division duplex (FDD) (Full duplex in analog systems) Time division duplex (TDD) (Half duplex in analog systems) 4 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Structure of the Physical Layer BB MAC RF L1 Protocol RRC 5 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
The UMTS FDD Frequencies The first allocation of the UMTS FDD system (ITU regions 1 & 3) is: 1920 1980 MHz up-link 2110 2170 MHz down link duplex distance 190 MHz The radio channel structure: 5 MHz channel spacing 200 khz channel raster UTRA absolute radio frequency channel number (UARFCN): (channel number = 5 x frequency in MHz) 6 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Modulation and Filtering Modulation method: Chip frequency 3.84 MHz QPSK I Q Filter Filter π/2 Filtering: Pulse shaping before modulation RRC with frequency domain roll-off 0.22 7 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA TX: Spreading Channelization within one frequency is achieved by representing bits as sequences of chips. 0 1 0 1 1 0 8 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA TX: Spreading The sequences are quasi-orthogonal between the channels. Combination of: Bit long orthogonal sequences (Walsh sequences), and Frame long pseudo noise sequences (Gold sequences) I Q 9 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA TX: Spreading The transmitted bits are paired, spread to a chip sequences using Walsh sequences and mapped to complex symbols. The complex symbols are scrambled by complex sequences formed of truncated Gold sequences. Even Bits I Bits Pairing Walsh code (I,Q) Pair to Complex (I + jq) Chips Odd Bits Q Complex Gold code 10 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA RX Receiving a CDMA transmission requires: Demodulation and filtering of the chip sequence. Correlating with the scrambling and spreading codes to detect the channel contents (chip sequence to bit sequence). The receiver also needs to remove: Noise Interference from other channels and frequencies Multi path propagation interference (fading) 11 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA RX: Rake Inter symbol interference due to multipath propagation. 12 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA RX: Rake Correlating the received chip stream with sequences delayed by the propagation time differences. Chips Delay Chips Integrate & dump Chips Delay Chips Scrambling sequence Chips Delay Chips Scrambling sequence Spreading Sequence Spreading Sequence Integrate & dump Integrate & dump Combining Bits Scrambling sequence Spreading Sequence 13 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Error Correction and Detection Convolutional codes, K = 9 Turbo code: PCCC, 2 x K=3 RCC's G 0 = 561 G 1 = 753 G 0 = 557 G 1 = 663 G 2 = 711 Interleaver CRC check sum: g CRC24 (D) = D 24 + D 23 + D 6 + D 5 + D + 1 g CRC16 (D) = D 16 + D 12 + D 5 + 1 g CRC12 (D) = D 12 + D 11 + D 3 + D 2 + D + 1 g CRC8 (D) = D 8 + D 7 + D 4 + D 3 + D + 1 14 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA FDD Transport Channels L1 provides the upper layers a variety of transport channels: Common channels BCH, the broadcast channel for system and cell information PCH, the paging channel FACH, the forward access channel for down-link connectionless random access communication. RACH, the random access channel for up-link random access communication. CPCH, the common packet channel for higher volume uplink packet communication. DSCH, the down-link shared channel for improving down link peak communication throughput. Dedicated channels DCH, the dedicated channel, for CS communication. 15 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA FDD Physical Channels Common channels CPICH PSCH SSCH PICH AICH AP-AICH CD/CA-ICH CSICH BCH PCCPCH PCH, FACH SCCPCH PDSCH DSCH Dedicated channels DCH DPCCH DPDCH Common channels PRACH PCPCH Dedicated channels DPDCH DPCCH RACH CPCH DCH 16 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
WCDMA FDD Frame and Slot Structure Frame: 10 ms, 38400 chips 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Slot: 2/3 ms, 2560 chips (example of DL DPCH) Data TPC TFCI Data Pilots 17 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Synchronization Synchronization... Acquire slot sync from PSCH Identify code group & frame sync from SSCH SSCH PSCH CPICH PCCPCH Identify scrambling code from CPICH PCCPCH (carries BCH)...Established 18 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Establishing Radio Link Cell information From BCH, tells parameters needed for establishing communication Paging From PCH when PICH indicates there is paging coming RACH/FACH RACH/AICH up-link using slotted aloha protocol reply on FACH DCH Will carry both communication and control data Paging during DCH comes on the DCCH 19 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Soft & Hard Hand-over Frequency A Frequency B 20 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
Soft & Hard Hand-over Node B 1 Node B 2 Node B 3 21 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
22 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
23 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
24 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
25 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
26 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
27 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
28 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org Soft & Hard Hand-over
WCDMA/GSM Hand-over GSM coverage area WCDMA coverage area 29 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org
30 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org WCDMA/GSM Hand-over
31 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org WCDMA/GSM Hand-over
32 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org WCDMA/GSM Hand-over
33 NOKIA 3gppl1.PPT/ 27-Sep-2000 / lapi@ieee.org WCDMA/GSM Hand-over