Title: Performance Analysis of a Preemptive and Priority Reservation Handoff Scheme for Integrated ServiceB
1Performance Analysis of a Preemptive and Priority
Reservation Handoff Scheme for Integrated
Service-Based Wireless Mobile Networksby Jingao
Wang, Quing-An Zeng, and Dharma P. Agrawal
- Presented by Okan Yilmaz
- CS 6204 Mobile Computing
- Virginia Tech
- Fall 2005
2Abstract
- Analytical Model Performance Analysis
- Call Types
- Originating calls
- Handoff requests
- Service Types
- Real-time
- Non-real-time
- Partitioning based system model
- Real-time service calls only
- Non-real-time service calls only
- Handoff requests only
- Preemptive priority handoff scheme
3Abstract (cont)
- Multidimensional Markov Model to estimate
- Blocking probability of originating calls
- Forced termination probability of handoff calls
- Average transmission delays
- Simulation and Performance Analysis
- Different call holding times
- Several cell dwell time distributions
- Results
- Significantly reduces the forced termination
probability of real-time calls - Negligible packet loss of non-real-time calls
4Introduction
- 2G Networks
- Limited and far from acceptable
- Voice
- Short message
- Low speed data
- 3G Networks
- Demand for Integrated services
- Business customers
- Any time, any place
- Employees, key customers
- e.g., brokerage, banking, emergency services,
traffic reporting, navigation, gambling, etc. - Wireless and VLSI Technology
- Multi-media-ready cell phones, pocket PCs, Palms
5Challenges of Integrated Services
- True combination of real-time and non-real-time
services - Maximize the utilization of network
infrastructure - Quality of service (QoS)
- Handoff handling
- Forced termination of an outgoing call is more
annoying than blocking of a new call
6Handoffs
- Handoff changing parameters of a channel
- Frequency, time slot, spreading code, or
combination of them - When crossing cell boundary or deteriorating
signal quality - Cell structure
- Support a drastic increase of demand
- Microcell, picocell, hybrid cell
- Smaller cells ? More handoffs
7Handoff Design Issues
- Forced termination versus new call blocking
- Increased channel utilization in a fair manner
- Goal
- Minimization of forced termination of real-time
service - Without drastically sacrificing the other QoS
parameters - Several studies based on voice based cellular
networks - Need for support of multiple service types
simultaneously - Keys for a good scheme
- Service dependent
- Delay sensitivity non-real-time versus real-time
- Preemptive model priority reservation handoff
8SYSTEM MODEL
- Homogenous cell with fixed number of S channels
- Reference cell approach
- Call types
- Real-time originating call MU dials a number to
place a real-time call - Real-time handoff request MU holding a channel
enters the handoff area - Non-real-time originating call MU places a
non-real-time call - Non-real-time handoff request Non-real-time MU
holding a channel approaches and crosses a cell
boundary - Cell boundary The points where the received
signal strength between two adjacent cells is
equal
9Notation
- ?OR arrival rate of real-time originating calls
- ?HR arrival rate of real-time handoff requests
- ?ON arrival rate of non-real-time originating
calls - ?HN arrival rate of non-real-time handoff
requests - RC real-time service channels group with
capacity SR - CC common handoff channels group with capacity
SC - NC non-real-time service channels group with
capacity SN - RT only In CC, real-time service channels
reserved exclusively for real-time handoff calls
with capacity SE - CH In CC, channels that can be used by both
real-time and non-real-time handoff calls with
capacity SC - SE - RHRQ real-time service handoff request queue
with capacity MR - NHRQ non-real-time service handoff request queue
with capacity MN
10System model for a reference cell
- ?OR ?RC(SR)
- ?HR ?RC(SR) ? HC(Sc-Sc) ? RT(SE) ? RHRQ(MR)
- ?HN ?NC(SN) ? HC(Sc-Sc) ? NHRQ(MN)
- ?ON ?NC(SN)
11Algorithm for Originating Calls
12Algorithm for Handoff Requests
13System Design (cont)
- Preemptive procedure real-time handoff request
calls preempt non-real-time handoff request calls
if a non-real-time in CC and NHRQ is not full - Real-time handoff requests may preempt
non-real-time handoff requests irrespective of
NHRQ being full or not - No need if very large NHRQ buffer
- Real-time handoff request are dropped
- If RHRQ is full (both RHRQ and NHRQ are full in
preemptive scheme) - If the handoff request in RHRQ cannot get
service until it moves out of the handoff area
14System Design (cont)
- Non-real-time handoff requests will never be
dropped - If NHRQ is large enough (not necessarily be
infinite) - Because the non-real-time handoff request is
transferred from the reference cell to another
cell - Waiting time in NHRQ dwell time of
non-real-time service subscribers - Real-time handoff request calls can continue
until signal strength becomes not enough to get
service - This is ignored in paper. It is assumed that the
call is blocked.
15Traffic Model
- Three characteristics
- Call arrival process
- Call holding time
- Cell dwell time
- Call arrival Poisson process
- Call holding time and cell dwell time
- Two approaches
- Traffic model general independent identically
distributed (i.i.d.) - Exponential, gamma, lognormal, hyper-exponential,
hyper-Erlang - Analytical model Users mobility, the shape and
size of the cell, and exponential distribution
are used to determine cell dwell and call holding
time - Paper uses the second for analytical modeling,
both for numerical and simulation results
16Dwell Time
- Two-dimensional fluid model
- fV(v) pdf of the speed V of MU
- EV mean of the speed of MU
- MU moves randomly any direction in 0,2?)
- Assumes uniform density of users
17Cell Dwell Time
- Biased sampling theory in boundaries 1
- ? density of MUs in the cell
- NO number of cell outgoing MUs with moving speed
v and v?v - NT total number of cell outgoing MUs per unit
time - A area of the cell
- L length of the perimeter
- ?dwell average outgoing rate of an MU within a
cell - Tdwell cell dwell time with a random exponential
distribution with mean 1/?dwell
18Handoff Area Dwell Time
- fV(v) pdf of the speed of real-time service
subscribers crossing cell boundary V - D the length of moving path of mobile users in
the handoff area - Th dwell time of real-time service subscribers
in the handoff area - ETh Average handoff area dwell time
- Path length and velocity of MUs are independent
19Channel Holding Time
- Exponential distribution
- TCR Call holding time of real-time calls
- TCN Call holding time of non-real-time calls
- ?CR Service rate of real-time calls
- ?CN Service rate of non-real-time calls
- TR Channel holding time of real-time service
calls - TN Channel holding time of non-real-time service
calls
20Arrival Process of Service Calls
- Poisson process
- ?OR arrival rate of real-time originating calls
- ?HR arrival rate of real-time handoff requests
- ?ON arrival rate of non-real-time originating
calls - ?HN arrival rate of non-real-time handoff
requests - Need to compute ?HR and ?HN from ?OR and ?ON,
respectively - Homogenous mobility pattern
- Mean number of incoming handoffs to reference
cell mean number of outgoing calls from the
reference cell
21Arrival Process of Service Calls (cont)
- ECR average number of real-time calls holding
channels in the reference cell - ?OUTR departure rate of real-time handoff calls
from the reference cell
22Arrival Process of Service Calls (cont)
- ENN average number of both non-real-time
service requests and calls in the reference cell - ECN average number of non-real-time MUs
holding channels in the reference cell - ELN average length of NHRQ
- ? total arrival rate of calls
23M/M/3/3
- M/M/3/3 2
- M Exponential or Poisson arrivals
- M Exponential or Poisson service
- 3 Number of servers
- 3 Maximum number of customers in the system
- P0 P1 P2 P31
- (??) P1 ? P0 2? P2
- Pblocking P3
- Throughput (1-P3) ?
24PERFORMANCE ANALYSIS
i
j
k
m
l
25Stable State diagram for (i1, j1, k1, l2, m0)
S SR SC SN 12 SR 6 SCSN3 SE1 MR5
MN50 NT3162
26Total number of states
- Four cases to consider
- Both RHRQ and NHRQ are empty
- 0 i SR0 j Sc - k 0 k Sc - SE 0 l
SN m 0 - k0 ? j(0 .. Sc) Sc 1 possibilities
- k1 ? j(0 .. Sc -1) Sc possibilities
-
- k Sc-SE ? j(0 .. SE) SE 1 possibilities
- Total (Sc-SE 1) (Sc SE 2)/2 states
- N1(SR1)(Sc-SE 1)(Sc SE 2)(SN1)/2
states - RHRQ is not empty while NHRQ is empty
- i SR Sc lt j k
- i SR Sc-k1 j Sc MR k 0 k Sc-SE
0l SN m0 - k0 ? j(Sc 1 .. Sc MR) MR possibilities
- k1 ? j(Sc .. Sc MR 1) MR possibilities
-
- k Sc-SE ? j(SE 1.. Sc MR) MR
possibilities - Total (Sc - SE 1) MR states
- N2(Sc - SE 1) MR (SN 1)/2 states
27Total number of states (cont)
- RHRQ is empty NHRQ is not empty
- Sc-SE j k l SN
- 0i SR Sc-SE-k j Sc-k 0k Sc-SE lSN
1m MN - k 0 ? j(Sc - SE .. Sc) (SE 1) possibilities
- k 1 ? j(Sc SE - 1 .. Sc - 1) (SE 1)
possibilities -
- k Sc - SE ? j(0 .. SE) (SE 1) possibilities
- Total (Sc - SE 1) (SE 1) states
- N3 (SR 1) (Sc - SE 1) (SE 1) MN
- Both RHRQ and NHRQ are not empty
- i SR Sc lt j k l SN
- i SR Sc-k1 j Sc MR - k 0k Sc-SE
lSN 1m MN - k 0 ? j(Sc1 .. Sc MR) MR possibilities
- k 1 ? j(Sc .. Sc MR - 1) MR possibilities
-
- k Sc-SE ? j(SE 1.. SE MR) MR
possibilities - Total (Sc-SE 1) MR/2 states
- N4 (Sc-SE1) MR MN/2 states
28Normalizing Condition
- Both RHRQ and NHRQ are empty
- RHRQ is not empty while NHRQ is empty
- RHRQ is empty while NHRQ is not empty
- Both RHRQ and NHRQ are not empty
29Average number of calls
- ECR average number of real-time calls holding
channels in the reference cell - 13 i j real-time calls
- 24 RC is full SC-k real-time calls
- ENN average number of both non-real-time
service requests and calls in the reference cell - 12 k l non-real-time calls
- 34 RN is full SNk real-time calls m calls in
NHRQ
30Pseudo-code to solve (NT2) independent nonlinear
equations
31Blocking Probabilities
- Originating real-time calls are blocked when i
SR - Forced termination of real-time service handoff
requests - BHR Blocking probability
- MR is full
- DR dropping probability
- MR is not empty
32Channel and RHRQ buffer utilizations
- Utilizationmean channel used/ S
- ECN average number of calls holding channels
- 12 kl non-real-time calls
- 34 NC is full SNk real-time calls m calls in
NHRQ - RHRQ utilization mean number of channels in
RHRQ/MR - ELR average length of RHRQ
- 12 jk-SC real-time handoff requests waiting in
RHRQ
33NHRQ Buffer Utilization and Forced Termination
probability
- NHRQ utilization mean number of channels in
LHRQ/MN - ELN average length of NHRQ
- 12 m non-real-time handoff requests waiting in
NHRQ - Ph Probability that a real-time service call
triggers a handoff request in the reference cell - Real-time service call holding time gt the cell
dwell time - Phf Forced termination probability of real-time
handoff calls - (l-1) successful handoff followed by a forced
termination
34Transmission Delay of non-real-time service
- Td The lifetime transmission delay of
non-real-time service - Sum of Tws
- Tw transmission delay on non-real-time service
in each cell - Littles Law
- Mean waiting time mean number of customers in
queue / throughput - BON blocking probability of originating
non-real-time calls - 1 - PNC?SN
- ETS Average serving time of non-real-time
calls - (mean number of calls getting service in queue)
/ (total throughput) - BHN blocking probability of non-real-time
service handoff requests - NHRQ is full m MN
35Average transmission delay of non-real-time
service (cont)
- Nh average number of handoff per a non-real-time
handoff request - (delay due to Nh handoffs call holding time) by
average serving time - ETN average transmission delay of
non-real-time service - Handoff arrival probability times average delay
each handoff request ecounters
36Numerical and Simulation Results
- Integrated service homogenous cellular system
- Call arrivals
- Poisson
- Call holding and cell dwell times
- Scenario 1 exponentially distributed as in
performance analysis - Scenario 2 iid with Gamma distribution
- Cell and handoff area dwell times with ?? 1.5
- Call holding time with ?? 2
- Same mean value
- Cell shape hexagonal
- Each neighbor has equal probability to receive
handoff
37Simulation Results Comparison of QoS Parameters
- Scen1 and analytical analysis results are
consistent - lt 4 difference in BOR, BON, and Phf
- Accuracy of analysis is substantiated
- Scen1 and Scen2 results are comparable
- Phf Scen2 is 20 less
- BOR, BON Scen2 is 6 and 2 larger,
respectively - TN Scen2 is 28 less
- Reasonable Gamma has smaller standard deviation
- Parallel trend
- Analytical formula with tolerable error margins
- BOR, BON blocking probability of real-time
non-real-time service - Phf Forced termination probability of real-time
service calls - TN Transmission delay of non-real-time service
calls
38Simulation Results Performance Comparison of
real-time calls
- Schemes
- Standard guard channel (base)
- Priority reservation
- Preemptive priority handoff
- Higher QoS parameters when higher arrival rates
(lower service quality)
- Fhr Phr
- Priority and preemptive have 14.7 and 30.9
improvements over guard channel, respectively - BOR almost the same
- Priority especially with preemptive procedure is
effective in decreasing forced terminations
39Simulation Results Performance comparison of
non-real-time calls
- TN increases with higher traffic
- Guard channel performs better
- Channels available for non-real-time decreases
due to lower priority - Largest TN is 3.91sec. 6.5 of whole service
time - 31 decrease in forced termination probability is
more important - 7 increase in blocking probability of
originating non-real-time calls - Forced termination probability of non-real-time
is negligibly small - Proposed scheme is better in terms of the
performance
40Conclusions
- A handoff scheme is proposed
- Priority reservation
- Preemptive priority policy
- Analytical model for performance analysis has
been proposed - Simulation results match the analytical model
- Several QoS parameters have been evaluated
- Forced termination probability of handoff
requests of real-time calls can be decreased - Non-real-time service handoff requests do not
fail - A reasonable 6.5 transmission delay increase
41References
- 1 Priority handoff analysis, Vehicular
Technology Conference, 1993 IEEE 43rd, Xie, H.
Kuek, S., Page(s) 855-858, Digital Object
Identifier 10.1109/VETEC.1993.510945 - 2 CS5214 Course notes, Ing-Ray Chen, 2004.