Simulazione di protocolli a pacchetto per reti radiomobili: GPRS ed UMTS

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Simulazione di protocolli a pacchetto per reti
radiomobiliGPRS ed UMTS

• Alberto Bona, Maurizio Conti

Politecnico di Torino
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Simulator purposes

• Analyzing GPRS and UMTS performances on radio
  interface in presence of different traffic
  sources
• Implementing MAC layer source code for both GPRS
  and UMTS systems
• Comparing simulation and theoretical model
  results
• Creating a software instrument open to future
  developements and extensions

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Alberto Bona, Maurizio Conti
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Simulator description

• General features
• Simulation environment
• BTS features
• GPRS simulator structure
• BTS structure
• MS structure
• GPRS simulations
• traffic sources
• results

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General features

• Programming language C
• Simulator type synchronous events
• Main interest for higher layer protocol
  performances
• Simplified physical layer model
• Closed topology
• Simultaneous presence of UL and DL MS

REFERENCE DOCUMENTS

• ETSI and 3GPP standards technical papers

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Simulation environment

• Based on suburban model defined in UMTS 30.03
• Base station distance 6 or 1.5 km
• Cell radius 2 km or 500 m
• Simulations of other environments are not
  precluded
• changing base station distance and cell radius
• changing propagation model
• Users mobility
• Every position update, users step from current
  pixel to an adjacent one

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BTS features

• Each BTS can be equipped with both
  omnidirectional and sectorial antennas
• Irradiation diagram is specified by an input file
• Propagation model

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GPRS-BTS structure

• PRACH-controller
• responsible for MS UL access
• RSC-allocator
• responsible for resource allocation

• Dyn_matrix maintains information about Dynamic
  and Extended dynamic allocation (USF)
• Fixed_matrix stores channel occurrences (PRACH,
  PAGCH) and MS fixed-allocation
• PDCH status carries information about PDCH
  status (GSM or GPRS)
• Dyn, E-Dyn, Fixed_alloc implement allocation
  algorithms

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GPRS-BTS structure

• TX-allocator
• responsible for frame scheduling
• schedulation is performed at the beginning of
  each block
• transmission is performed frame by frame

• TX_matrix stores information about the block
  owner, either a controller or a MS
• Dyn, E-dyn, fixed_sched perform algorithms for
  PDCH condivision through RSC information

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GPRS MAC MS structure

• MAC-buffer stores MAC-blocks ready for
  transmission and controls access to uplink PDCH
• Header inserts header to RLC-PDU, updating
  fields for statistics
• PRACH-controller responsible for access
  procedures

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Simulations

• Validation test
• Resource sharing between GPRS and GSM (1
  carrier)
• GPRS traffic multiplexing on 1 PDCH
• GPRS traffic multiplexing on 7 PDCH

COMMON FEATURES

• Dynamic allocation
• Round-Robin schedulation

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GPRS traffic sources

• ON-OFF status length is negative exponentially
  distributed
• Mean time ON/OFF 20/40 s
• Mean time between packet 500 ms
• Packet length depends on offered bit rate
• 1.9, 6.4, 11.2, 19.2, 64 kbit/s (peak)
• CS3 coding scheme
• Packets are segmented by RLC and passed to MAC
  layer

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Performance parameters

• GPRS blocking probability
• GSM blocking probability
• Access delay (UL)
• MAC block transfer delay
• Session throughput
• IP packet throughput

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Validation test
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Resource sharing between GSM and GPRS (1 carrier)

• GSM sources
• Mean call length 1/m. 120 s
• Mean call interarrival time 1/l
• Offered load l/m M 2, , 8
• 100 users per cell
• GPRS sources
• Offered load per user 6.4, 11.2, 19.2 kbit/s
  (peak)
• 4 users per cell

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Resource sharing
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Resource sharing
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Resource sharing
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Resource sharing
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Only GPRS traffic multiplexing

• No GSM sources
• Multiplexing on 1 PDCH
• Offered load per user 1.9, 6.4, 11.2, 19.2
  kbit/s (peak)
• 1, 2, , 10 users per cell
• Multiplexing on 7 PDCH
• Offered load per user 11.2, 19.2 kbit/s (peak)
• 1, 5, 10, , 25 users per cell

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Multiplexing on 1 PDCH
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Multiplexing on 1 PDCH
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Multiplexing on 1 PDCH
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Multiplexing on 7 PDCH
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Multiplexing on 7 PDCH
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Multiplexing on 7 PDCH
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Multiplexing on 7 PDCH
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