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Queueing Priority Channel Assignment Strategies for PCS Hand-Off and Initial Access. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY,1994 Yi-Bing Lin, Seshadri Mohan, and Anthony Noerpel. Speaker: R01922021 趙祈鈞. Outline. Introduction Related Works Analytic Models Traffic Model

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queueing priority channel assignment strategies for pcs hand off and initial access

QueueingPriority Channel Assignment Strategies for PCS Hand-Off and Initial Access

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY,1994

Yi-Bing Lin, Seshadri Mohan, and Anthony Noerpel

Speaker: R01922021 趙祈鈞

outline
Outline
  • Introduction
  • Related Works
  • Analytic Models
    • Traffic Model
    • System Model
  • Simulation
  • Conclusions
introduction
Introduction
  • Personal Communication Service(PCS)
    • Cells and channels
    • Provides wireless access to PSTN
    • Hand-off, or Automatic Link Transfer(ALT)
  • PCS radio systems
    • DECT, CT-2 Plus (with signaling channel)
    • WACS (directly on traffic channel)
introduction1
Introduction
  • ALT strategies
    • Portable-controlled
      • DECT, WACS
    • Network-controlled
      • CT-2 Plus
    • Portable-assisted
  • ALT-initial access channel assignment schemes
    • Non-prioritized scheme (NPS) and Guard channel
introduction2
Introduction
  • ALT-initial access channel assignment schemes
    • FIFO //degradation interval
    • Measured-based priority scheme (MBPS)
      • FIFO scheme with different queueing policy
related works
Related Works
  • Hong and Rappaport [10] //FIFO
    • Based on a special portable movement pattern by Poisson process
  • Tekinary and Jabbari [17] //FIFO
    • Td normally distributed, Markov chain
    • [9] says expo. dist. is more suitable for Markov chain
    • Considered the hand-off traffic as an indep. input (X)
  • Yoon and Kwan [19]
    • hand-off traffic as an indep. input (X)
    • M/M/C/K instead of timeout system
  • This paper
    • NPS, FIFO and MBPS, 50/10 servers per cell
analytic models traffic
Analytic Models (Traffic)
  • A portable moves across K cell boundaries
    • Also # of hand-offs
  • Call holding time: tc (expo.) density:
  • Start at R0, visits K cells, tM_i: time in i-th cell
  • Time of R0 to 1: tm, density:
  • tMi is i.i.d., dist.: density: mean:
traffic model
TrafficModel
  • By Random Observer Property(ROP) of Poisson
  • For K>=1,
traffic model1
Traffic Model
  • Use (1) and (2),
  • with Laplace transform
traffic model2
Traffic Model
  • Let be an exponential distribution
    • M/G/c => M/M/c ,so
    • Hand-off call arrival rate
traffic model3
Traffic Model
  • Pc: prob{call completed}
  • If
  • If
  • Obs. of Hong and Rappaport [10] not general
    • Pnc is more sensitive to Po than to Pf (X)
    • From (10), ↑
analytic models system
Analytic Models(system)
  • For NPS,
  • For FIFO
    • t_d: expo.
      • Mean:
system model for nps
System Model for nps
  • t_co = min(t_c, t_m) //t_channel occupancy =

min(t_call holding, t_remaining portable residual)

system model for nps1
System Model for nps
  • From the Erlang-B formula
    • For lost systems (no queue)
    • Total traffic load
      • Avg. arrival rate
      • Avg. service rate
  • NPS:
system model for fifo
System Model for fifo
  • FIFO
  • t_q = min(t_d, t_m) //t_maxqueueing =

min(t_timeout, t_remaining portable residual)

    • A hand-off call is blocked

if no channel is assigned

before t_maxqueueing

  • density:
system model for fifo1
System Model for fifo
  • State s(n), n>=0
    • n: # of busy channels
  • For 0<=n<c
    • S(n) has n busy channels, no HO in queue
  • For n=c+j>=c
    • All c channels busy, j HOs in queue, new calls dropped
system model for fifo2
System Model for fifo
  • Steady state probability for s(n)
system model for fifo3
System Model for fifo
  • Prob{originating call blocked}
  • Prob{hand-off call blocked}
    • Let a hand-off call Ct arrives at t in state s(n)
    • //n=c+j, so Ct will be in queue
    • Suppose the 1st call leaves the queue at t+tj
    • Ct needs to wait for j+1 calls before him.
system model for fifo4
System Model for fifo
  • E[waiting time]
simulation
Simulation
  • Discrete event simulation model
    • 1st chooses a
    • Simulates to obtain Po and Pf
    • Use (9) to compute new lambda_h
    • Repeat until lambda_h converges
  • 3 types of events
    • ARRIVAL
      • originating or hand-off
    • COMPLETION
      • Calls releasing channels (completes or portable moves)
    • WAIT
simulation1
Simulation
  • Sim_count: N
  • Record No, Nf
  • Initial, gen 1st
  • Max N: 800,000
  • ARRIVAL
    • o or h: rand()
  • (13) Iter. ends
  • (10) e1:timeout(11)
analysis vs simulation
analysis vs. Simulation
  • Plot Pf, Po, Pnc and normalized E[waiting]
  • c=50, 1/miu=3min, 1/gamma=18s, 1/eta=30min
  • Compare with [17]
    • Pf and Po for MBPS always < that for FIFO (X)
simulation2
Simulation
  • NPS vs. FIFO
  • c=10, 1/miu=3min

1/eta=10min

1/gamma=18s, 55s

  • (c): Pr[f|nc]
  • FIFO
    • Better w/ small gamma
    • Pf↓ Pnc little↓
    • because Po little↑
conclusions
Conclusions
  • Proposed analytic and simulation models to study ALT-initial access channel assignment schemes(NPS, FIFO, MBPS).
    • Major output measures: Po, Pf, Pnc
  • Vs. Hong and Rappaport [10]
    • Pnc is more sensitive to Po than to Pf (X general)
    • Indicated if mobility↑, impact of Pf on Pnc↑, of Po↓
  • Vs. Tekinary and Jabbari [17]
    • MBPS provides lower Pf and Po (X)
    • Indicate that MBSP and FIFO roughly the same(Pf, Po)
  • FIFO significantly Pf↓, slightly Po↑
    • Yield slightly better (smaller) Pnc //vs. NPS