Mobile IPTV services over wireless cellular networks become more and more popular, owing to the significant growth in access bandwidth of wireless cellular networks such as 3G/4G and WiMAX. However, the spectrum resources of wireless cellular networks is rare. How to enhance the spectral efficiency of mobile networks becomes an important issue. Unicast, broadcast, and multicast are the most important transport schemes for offering mobile IPTV services over wireless cellular networks. Therefore, bandwidth usages and blocking rates of unicast, broadcast, and multicast IPTV services were analyzed and compared in this paper. Simulations were also conducted to validate the analytical results. Numerical results demonstrate that the presented analysis is correct, and multicast scheme achieves the best bandwidth usage and blocking rate performance, relative to the other two schemes.
Internet protocol television (IPTV) services have been becoming increasingly popular among telecommunication companies [
Three basic transport technologies including unicast, broadcast, and multicast can be adopted for delivering mobile IPTV streams. Unicast technology provides one-to-one connection between the base station and the mobile user. Whenever a mobile user requests to watch a TV channel, the base station must establish a dedicated connection for this mobile user if his request is accepted. Even though two mobile users request to watch the same TV channel program, two independent connections must be established, yielding unnecessary bandwidth consumption. To overcome this shortcoming, the broadcast technology [
The performance superiority of the transport schemes mentioned above is related to traffic conditions of networks. Therefore, to optimize the resource usage of wireless cellular networks, a hybrid unicast-broadcast delivery scheme was proposed and discussed in [
The contributions of this work are summarized as follows. Firstly, the user request arrival process, the channel watching time, the channel popularity, the number of available channels, and the limited time-frequency resources are simultaneously considered in the analysis. Secondly, an exact queuing analysis method is introduced to derive blocking rates and bandwidth usages of unicast, broadcast, and multicast IPTV services over wireless cellular networks. Thirdly, simulations are also conducted for validating the correctness of the analysis. Finally, network providers can use the analytical results to design their networks to operate in a more efficient and cost-effective manner.
The rest of this paper is organized as follows. Section
In addition to traditional voice and data services, mobile IPTV services must also be supported in modern mobile networks. Effective performance analysis for mobile networks that simultaneously support voice, data, and IPTV services is still intractable now. However, since mobile IPTV services require extra large bandwidth compared with voice and data services, the performance of mobile networks is significantly dominated by mobile IPTV traffic. Thus, to make the performance analysis problem tractable, in the first stage a simpler mobile network system in which the dedicated time-frequency resources for voice/data traffic and mobile IPTV traffic are completely separated is assumed. That is, in this paper the voice and data traffic are ignored and only the performance of IPTV services is analyzed.
To understand the effects of mobile IPTV services on the performance of mobile networks, the following queuing model is presented and analyzed. The considered queuing system in this paper is limited to within a cell of the mobile network since the network operation of each cell is similar. The terminology
For broadcast IPTV services, each broadcasted TV channel always occupies a unit of bandwidth resources even though no users watch the channel. Since the total amount of bandwidth resources for mobile IPTV services is
Next, the bandwidth usage
For unicast IPTV services, each accepted TV request can be served by using an individual connection between the mobile user and the base station. Therefore, the system in a cell can be simply modeled as an
For the special case of homogeneous service rates
For the case of uniform hit rate distribution
When
Subsequently, let us consider the blocking case
State transition diagram.
When the system is in state
When the system is in state
It is difficult to solve the stationary state probability
Accordingly, the stationary state probability
For all states
Since the sum of all stationary state probabilities must be equal to 1, the following equation must hold:
In this section, blocking rates and bandwidth usages of unicast, broadcast, and multicast IPTV services based on the analytical results given in previous sections are evaluated. Simulation results are also given for verification. In addition, the effects of hit rate distribution on the performance are investigated as well. Several hit rate distributions, such as uniform and Zipf-like [
In the first example, homogeneous service rates are considered, that is,
Blocking rates of unicast, broadcast, and multicast IPTV services. (Hit rate distribution: uniform.)
Bandwidth usages of unicast, broadcast, and multicast IPTV services. (Hit rate distribution: uniform.)
In the second example, the hit rate distribution is assumed to follow the Zipf-like distribution. That is, the hit rate is distributed according to the formula
Blocking rates of unicast, broadcast, and multicast IPTV services. (Hit rate distribution: Zipf-like distribution with
Bandwidth usages of unicast, broadcast, and multicast IPTV services. (Hit rate distribution: Zipf-like distribution with
Based on the previous two examples, the performance of broadcast and multicast schemes is related to the hit rate distribution. Therefore, the effects of hit rate distribution on the performance of IPTV services are studied herein. The system parameters are set the same as those in the first example except for the hit rate distribution. Figure
Blocking rates of broadcast and multicast IPTV services under different hit rate distributions.
Bandwidth usage of multicast IPTV services under different hit rate distributions.
Finally, the performance of unicast and multicast services under the scenario of heterogeneous service rates is studied. In the following, the service rate
Blocking rates of unicast and multicast IPTV services under the scenario of heterogeneous service rates. (Hit rate distribution: uniform.)
Bandwidth usages of unicast and multicast IPTV services under the scenario of heterogeneous service rates. (Hit rate distribution: uniform.)
Blocking rates and bandwidth usages of unicast, broadcast, and multicast IPTV services over wireless cellular networks are analyzed in this paper. In our analysis, the arrival process of TV channel requests, channel watching time, and channel popularity are concurrently considered. The analytical results are validated to be correct by simulations. The effects of channel hit rates on the performance of mobile IPTV services are also investigated in the numerical results. Based on the numerical results, multicast scheme is shown to be the best scheme for providing mobile IPTV services over wireless cellular networks from the viewpoints of blocking rate and bandwidth usage. Namely, using multicast scheme to offer mobile IPTV services can minimize the blocking rate and at the same time improve the spectral efficiency of wireless cellular networks. The analytic results in this work can be employed for precise resource allocation and service planning in wireless cellular networks that support mobile IPTV services.
The analytical results derived in this paper are based on the assumption that the bandwidth overheads of unicast, broadcast, and multicast schemes are the same. If the bandwidth overheads of unicast and multicast schemes are different [
The author declares that there is no conflict of interests regarding the publication of this paper.
This work was supported by NSC of Taiwan under Grant no. NSC102-2221-E-182-002-MY2.