09-07-2012, 03:11 PM
Call Admission Control for QoS Provisioning in 4G Wireless Networks: Issues and Approaches
[attachment=27283]
A Mobility-Based Approach
Mobility-based approaches exploit user mobility information
for efficient CAC. For example, the shadow clustering concept
was introduced in [7] based on user mobility information to
estimate future resource requirements in a microcellular wireless
network. The idea here is that every mobile terminal with
an active wireless connection exerts an influence on the cells
in the vicinity of its current location and along its direction of
travel. To calculate the shadow cluster and the corresponding
levels of intensity, the information on call holding time, current
direction, velocity, and position of the active mobile terminal
need to be considered.
Call Admission Control in CDMA Systems
Due to the soft-capacity feature, the admission control decision
in a CDMA network should be based on the state of
ongoing calls (e.g., interference level). The CAC approaches
used in hard-capacity systems based on the assumption of
time-invariant cell capacity may degrade the system utilization
in a CDMA system. Also, due to the soft handoff feature, the
length of a handoff process becomes longer than that of hard
handoff, and the CAC algorithm must take this duration into
account.
A Pricing-Based Approach
A pricing-based approach to CAC was proposed in [8], where
the objective is to maximize the utility of wireless resources.
Utility is generally defined as the users’ level of satisfaction
with perceived QoS. For example, utility is a decreasing function
of new call blocking and handoff call dropping probabilities
(i.e., Pnb and Phd, respectively). However, maximizing the
utility of the network might not maximize the revenue of the
service provider. Specifically, for higher user satisfaction,
more resources should be allocated to each user. In contrast,
to maximize revenue under flat rate pricing, the allocations
need to be degraded to accommodate more users. Therefore,
a CAC scheme can be designed such that the optimal operating
point can be obtained.
Multiple Classes of Services and Interoperability with DiffServ-Based IP Networks
CAC algorithms should be designed to support multiple classes
of services, each with specific QoS requirements. The service
classes can be chosen to be similar to those used in
differentiated services (DiffServ) [10] IP networks. This would
enable seamless integration of wireless networks with the IPbased
Internet.
DiffServ is one of the key technologies for providing QoS in
the Internet. Instead of providing QoS on a per-flow basis as
in the integrated services (IntServ) model, DiffServ operates
on groups of flows by aggregating several IP-level flows with
the same QoS requirements into the same group. By using the
type of service (TOS) field in the IP packet header, DiffServ
routers can identify the group to which an IP packet belongs
and then use appropriate traffic management schemes so that
the QoS requirements can be satisfied at the aggregate level.
[attachment=27283]
A Mobility-Based Approach
Mobility-based approaches exploit user mobility information
for efficient CAC. For example, the shadow clustering concept
was introduced in [7] based on user mobility information to
estimate future resource requirements in a microcellular wireless
network. The idea here is that every mobile terminal with
an active wireless connection exerts an influence on the cells
in the vicinity of its current location and along its direction of
travel. To calculate the shadow cluster and the corresponding
levels of intensity, the information on call holding time, current
direction, velocity, and position of the active mobile terminal
need to be considered.
Call Admission Control in CDMA Systems
Due to the soft-capacity feature, the admission control decision
in a CDMA network should be based on the state of
ongoing calls (e.g., interference level). The CAC approaches
used in hard-capacity systems based on the assumption of
time-invariant cell capacity may degrade the system utilization
in a CDMA system. Also, due to the soft handoff feature, the
length of a handoff process becomes longer than that of hard
handoff, and the CAC algorithm must take this duration into
account.
A Pricing-Based Approach
A pricing-based approach to CAC was proposed in [8], where
the objective is to maximize the utility of wireless resources.
Utility is generally defined as the users’ level of satisfaction
with perceived QoS. For example, utility is a decreasing function
of new call blocking and handoff call dropping probabilities
(i.e., Pnb and Phd, respectively). However, maximizing the
utility of the network might not maximize the revenue of the
service provider. Specifically, for higher user satisfaction,
more resources should be allocated to each user. In contrast,
to maximize revenue under flat rate pricing, the allocations
need to be degraded to accommodate more users. Therefore,
a CAC scheme can be designed such that the optimal operating
point can be obtained.
Multiple Classes of Services and Interoperability with DiffServ-Based IP Networks
CAC algorithms should be designed to support multiple classes
of services, each with specific QoS requirements. The service
classes can be chosen to be similar to those used in
differentiated services (DiffServ) [10] IP networks. This would
enable seamless integration of wireless networks with the IPbased
Internet.
DiffServ is one of the key technologies for providing QoS in
the Internet. Instead of providing QoS on a per-flow basis as
in the integrated services (IntServ) model, DiffServ operates
on groups of flows by aggregating several IP-level flows with
the same QoS requirements into the same group. By using the
type of service (TOS) field in the IP packet header, DiffServ
routers can identify the group to which an IP packet belongs
and then use appropriate traffic management schemes so that
the QoS requirements can be satisfied at the aggregate level.