Cognitive Radio Networks

Chapter 5

White Space A llocation in

a Co gnitive Radio-Based

High-Speed Vehicle

Network

It is well kn own th at high-speed vehicles, such as high-speed trains, are playing an

increasingly impor ta nt role in people’s lives, since they provide a rela tively stable and

spacious environment f or long distanc e travelers. As a resu lt, there is a strong dema nd

for broadband wireless communications (BWC) f or high-speed vehicles to provide

informa tion access and onboar d entertainme nt services for passengers. However, the

cognitive radio network sho uld be employed to overcome the problem of spectrum

scarcity.

For a cognitive radio network, primary c hannel oc cupancy modeling is very im-

portant for designing secondary user spectrum accessing and scheduling schemes.

PUs in different primary networks usually have different activity mod els, such as in

a cellular network [76], w ireless loc al area network (WLAN) [27], TV/broadca sting

network [7 7], and so forth. However, the existing literature is concerned about static

or low-speed mobile users, and do not consider situations with high-speed mobile

users, in which, the channel availabilities are very different due to the high velocity

of users [78, 79].

75

76 

Cognitive Radio Networks

In this chapter, high-speed vehicles are considered for employing the

TV/broadcasting b and via cognitive radio technology to achieve broad band wireless

communications [106]. In a high-speed moving scenario, primary channel occupancy

is mainly depende nt on the secondary user’s position, moving speed, and direction.

Therefore, the relative prim ary channel occupancy m odel, which mainly depends on

the vehicle’s location, velocity, moving directio n, and so on, is considered. Moreover,

a co gnitive r adio-based high-speed vehicle network (CR-HSVN) is introduced and a

framework of the spectrum resource allocation is introduced for effectively utilizing

TV white space.

5.1 A Cognitive Radio-Based High-Speed

Vehicle Network

5.1.1 System Model

In this chapter, we employ the following terms: (1) primary base station (PBS): the

TV signal transmission tower; (2) primary user (PU): the TV set; (3) cognitive base

station (CBS): the CBSs are deployed in the considered area similar to the base sta-

tions in the cellular network, and are m anaged a nd operated by wireless ope rators;

(4) co gnitive vehicle (CV): high-speed vehicle; and (5) cognitive user (CU): the pas-

senger in the CV that needs to access the cogn itive radio network. The main variables

are listed in Table 5.1.

As shown in Figure 5.1 , we assume that there are L PBSs in a certain area, de-

noted as P

l

,l = 1,2,··· ,L. N primary chan nels, denoted as C

n

, n = 1, 2,··· ,N, are

assigned to PBSs to provide services for PUs in the ir coverage ranges. Each PBS

P

l

occupies a fixed and known primary channel C

n

. Note that whe n N 6 L, differ-

ent PBSs may use the same primary channel if they are far away fro m each other.

Locations of these PBSs are known. The coverage radius r

l

of P

l

may be differ-

ent for d ifferent PBSs according to the actu al demand. The PBSs with overlap ped

r

TV signal

transmitter tower

Cognitive

base station

Figure 5.1: The scenario of CR-based high-speed vehicle communication s.