GPRS simulator

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

      Alberto Bona, Maurizio Conti


  Politecnico di Torino
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

                                                2
    Alberto Bona, Maurizio Conti
Simulator description
 General features
 Simulation environment
 BTS features
 GPRS simulator structure
    – BTS structure
    – MS structure
   GPRS simulations
    – traffic sources
    – results

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       Alberto Bona, Maurizio Conti
  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
                                                  4
        Alberto Bona, Maurizio Conti
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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         Alberto Bona, Maurizio Conti
    BTS features
   Each BTS can be
    equipped with both
    omnidirectional and
    sectorial antennas
   Irradiation diagram is
    specified by an input file
   Propagation model:


            GmsGbts
    Pr  Pt                             Atot   dB
                                                     Apr         Ash dB  Af
             Atot                                           dB                   dB


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         Alberto Bona, Maurizio Conti
                                                   GPRS-BTS Model
      MS’stack                                                                   PRACH-contr olle r
                                                              Target MS
     list in BTS
                                                                                         Waiting
        TX          IDLE      waiting                                                    MS-list


      MAC           MAC       MAC                                    MAC                           To MS
                                                                 Buffer
       Buffer      Buffer      Buffer                             RX
        TX          TX          TX                                                     PRACH
                                          Peer
                                         pointer                                      management
                                         to RX-
                                         Buffer

RSC-allocator                                                              TX-allocat or

                   DYN.              E-DYN.          FIXED                                 DYN.            E-DYN.        FIXED
                   alloc              alloc           alloc                                sched            sched         sched

 To Buffer
                                                                                                   52 frame with 12 b locks
    TX
                                                                                           B0 B1     B2
       PDCH0                     1
                                                                                 PDCH0
                                 1

fi                                                                          fi
                                 1

       PDCH7                     0                                                PDCH7
           USF          USF   PDCH        Block              Block
             0           7    status        0                  11
                 Dyn                               Fixed                                 Schedulation
                mat rix                            mat rix                                  points                            7
GPRS-BTS structure                                MS’stack
                                                 li st in BTS

                                                    TX



                                                  MAC
                                                   Buffer
                                                    TX
                                                                 IDLE



                                                                 MAC
                                                                Buffer
                                                                 TX
                                                                           waiting



                                                                           MAC
                                                                            Buffer
                                                                             TX
                                                                                       Peer
                                                                                                GPRS-BTS Model
                                                                                                           Target MS




                                                                                                                  MAC
                                                                                                              Buffer
                                                                                                               RX
                                                                                                                              PRACH-contr olle r

                                                                                                                                      Waiting
                                                                                                                                      MS-list




                                                                                                                                    PRACH
                                                                                                                                                To MS


                                                                                      pointer                                      management
                                                                                      to RX-




   PRACH-controller:
                                                                                      Buffer

                                            RSC-allocator                                                               TX-allocat or

                                                                DYN.              E-DYN.          FIXED                                 DYN.            E-DYN.        FIXED
                                                                alloc              alloc           alloc                                sched            sched         sched

                                             To Buffer
                                                                                                                                                52 frame with 12 b locks
                                                TX




    – responsible for MS UL access
                                                                                                                                        B0 B1     B2
                                                   PDCH0                      1
                                                                                                                              PDCH0
                                                                              1

                                            fi                                                                           fi
                                                                              1

                                                   PDCH7                      0                                                PDCH7
                                                       USF           USF   PDCH        Block              Block
                                                         0            7    status        0                  11
                                                             Dyn                                Fixed                                 Schedulation




   RSC-allocator:
                                                            mat rix                             mat rix                                  points




    – 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                                       8
         Alberto Bona, Maurizio Conti
                                                                                              GPRS-BTS Model



GPRS-BTS structure                              MS’stack
                                               li st in BTS

                                                  TX



                                                MAC
                                                 Buffer
                                                  TX
                                                               IDLE



                                                               MAC
                                                              Buffer
                                                               TX
                                                                         waiting



                                                                         MAC
                                                                          Buffer
                                                                           TX
                                                                                     Peer
                                                                                    pointer
                                                                                    to RX-
                                                                                                         Target MS




                                                                                                            Buffer
                                                                                                             RX
                                                                                                                MAC
                                                                                                                            PRACH-contr olle r

                                                                                                                                    Waiting
                                                                                                                                    MS-list




                                                                                                                                  PRACH
                                                                                                                                 management
                                                                                                                                              To MS




                                                                                    Buffer

                                          RSC-allocator                                                               TX-allocat or

                                                              DYN.              E-DYN.          FIXED                                 DYN.            E-DYN.        FIXED
                                                              alloc              alloc           alloc                                sched            sched         sched

                                           To Buffer




   TX-allocator:
                                                                                                                                              52 frame with 12 b locks
                                              TX
                                                                                                                                      B0 B1     B2
                                                 PDCH0                      1
                                                                                                                            PDCH0
                                                                            1

                                          fi                                                                           fi
                                                                            1

                                                 PDCH7                      0




     – responsible for frame scheduling
                                                                                                                             PDCH7
                                                     USF           USF   PDCH        Block              Block
                                                       0            7    status        0                  11
                                                           Dyn                                Fixed                                 Schedulation
                                                          mat rix                             mat rix                                  points




     – 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

                                                                                                                                      9
       Alberto Bona, Maurizio Conti
    GPRS MAC MS structure
   MAC-buffer: stores
    MAC-blocks ready for                  GPRS-MAC-MS-TX model
                                                               RLC
    transmission and
    controls access to                    PRACH                                   Standard
    uplink PDCH                          controller
                                                               Header
                                                                                 algorithms



   Header: inserts header                            MAC              TX
                                                                                               PEER
                                                                                               MAC
                                                      buffer        controller
    to RLC-PDU, updating
    fields for statistics
   PRACH-controller:
    responsible for access                                      PHY

    procedures

                                                                                              10
          Alberto Bona, Maurizio Conti
    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
                                          11
       Alberto Bona, Maurizio Conti
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

                                               12
       Alberto Bona, Maurizio Conti
Performance parameters
   GPRS blocking probability
   GSM blocking probability
   Access delay (UL)
   MAC block transfer delay
   Session throughput
   IP packet throughput



                                     13
      Alberto Bona, Maurizio Conti
Validation test
                                         PRACH access delay

 1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

 0
      0         50                100            150          200   250

                                                Frames



                                                                          14
          Alberto Bona, Maurizio Conti
    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

                                                      15
           Alberto Bona, Maurizio Conti
Resource sharing
                            GPRS blocking probability - UPLINK

   1




  0.1
                                                                     GSM
                                                                     6.4 kbit/s
                                                                     11.2 kbit/s
                                                                     19.2 kbit/s
 0.01




0.001
        2              3           4       5    6       7        8
                                           M


                                                                        16
            Alberto Bona, Maurizio Conti
Resource sharing
                           GPRS blocking probability - DOWNLINK

   1




  0.1
                                                                      GSM
                                                                      6.4 kbit/s
                                                                      11.2 kbit/s

 0.01                                                                 19.2 kbit/s




0.001
        2              3            4      5    6       7         8
                                           M


                                                                         17
            Alberto Bona, Maurizio Conti
Resource sharing
                                 MAC transfer delay - UPLINK

     4000

     3500

     3000

     2500
                                                                   6.4 kbit/s
ms




     2000                                                          11.2 kbit/s
                                                                   19.2 kbit/s
     1500

     1000

     500

       0
              2           3           4    5      6       7    8
                                           M


                                                                       18
            Alberto Bona, Maurizio Conti
Resource sharing
                                  Session throughput - UPLINK

         16

         14

         12

         10
                                                                    6.4 kbit/s
kbit/s




         8                                                          11.2 kbit/s
                                                                    19.2 kbit/s
         6

         4

         2

         0
              2           3           4      5     6      7     8
                                             M


                                                                       19
              Alberto Bona, Maurizio Conti
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

                                                    20
      Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
                          MAC transfer delay - DOWNLINK

     20000

     15000
                                                                 1.9 kbit/s
                                                                 6.4 Kbit/s
ms




     10000
                                                                 11.2 kbit/s
     5000                                                        19.2 Kbit/s


        0
               1      2      3      4   5   6   7   8   9   10
                                        Users


                                                                       21
         Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
                              Session throughput - DOWNLINK

         16
         14
         12
                                                                      1.9 kbit/s
         10
kbit/s




                                                                      6.4 kbit/s
         8
                                                                      11.2 kbit/s
         6
                                                                      19.2 Kbit/s
         4
         2
         0
               1      2       3      4       5   6   7   8   9   10
                                             Users


                                                                            22
              Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
                               Packet throughput - DOWNLINK

         18
         16
         14
         12                                                           1.9 kbit/s
kbit/s




         10                                                           6.4 kbit/s
          8                                                           11.2 kbit/s
          6                                                           19.2 kbit/s
          4
          2
          0
               1      2       3      4       5   6   7   8   9   10
                                             Users


                                                                            23
              Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
                                               Access delay

     180
     160
     140
     120
     100                                                                11.2 kbit/s
ms




      80                                                                19.2 kbit/s
      60
      40
      20
       0
               1            5             10           15     20   25
                                               Users


                                                                             24
           Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
                               MAC transfer delay - DOWNLINK

     1200

     1000

      800
                                                                       11.2 kbit/s
ms




      600
                                                                       19.2 kbit/s
      400

      200

        0
                 1            5            10           15   20   25
                                                Users


                                                                            25
            Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
                                 Session throughput - DOWNLINK

         20
         18
         16
         14
         12
kbit/s




                                                                         11.2 kbit/s
         10
          8                                                              19.2 kbit/s
          6
          4
          2
          0
                1            5               10           15   20   25
                                                  Users


                                                                              26
              Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
                                    Packet throughput - DOWNLINK

         100
          90
          80
          70
          60
kbit/s




                                                                          11.2 kbit/s
          50
          40                                                              19.2 kbit/s
          30
          20
          10
           0
                  1             5             10           15   20   25
                                                   Users


                                                                               27
               Alberto Bona, Maurizio Conti

				
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