**6.2.3 Wireless Metropolitan Area Network (WMAN)**

WiMAX, GPRS, GSM, CDMA and 3G mobile Carrier services are four WMAN technologies, which are used for WMAN communication. The descriptions of these technologies are as follows:

**WiMAX**: Worldwide Interoperability for Microwave Access (WiMAX) is a communication protocol, which provides fix and fully mobile data networking. WiMAX is based on the IEEE 802.16 standards and its most popular one is 802.16e-2005. Unlike WLAN technologies e.g. Wi-Fi, WiMAX is designed to operate as a WMAN. Various kinds of WiMAX work with both FCC licensed frequencies and unlicensed frequencies. Licensed WiMAX works in the range of 10 to 66 GHz and unlicensed WiMAX works in the range of 2 to 11 GHz. WiMAX theoretical data rate is 70 Mbps with a range of up to a maximum of 50 km with a direct line of sight (LOS). Near line of sight (NLOS) conditions seriously limit their range (Fourty et al., 2005; Shahraeini et al., 2010).

Wide Area Measurement Systems 319

**Low Earth Orbit (LEO)** satellites rotate between 750 and 1500 kilometers orbit. LEO satellites are widely used for communications. Iridium, Globalstar and Orbcomm are some

**Medium Earth Orbit (MEO)** satellites are at altitudes between nearly 10,000 and 20,000 kilometers. From the view point of the earth, MEO rotate slowly in longitude; feel like 6

These three types of satellites cover surface of the earth almost everywhere, hence; WWAN technologies provide remote sites connections. Although satellites can connect remote sites to the control center, high latency of these connections may create serious problems for some WAMS applications. As a result of this, some critical applications such as WAPS (Wide Area

To be able to obtain a global comparison among different transmission media used in power system communications, the above mentioned transmission media are compared based on

Media Type Media Bandwidth Latency Security

It should be noted that the above mentioned transmission media may be used either for WAMS communications or for other communications of the system (e.g. SCADA). But the important concept is that the communication infrastructure of WAMS is the most extensive communication infrastructure in a power system. Other communications (e.g. SCADA and SPMS) may be a part of the communication infrastructure of WAMS. Modern communication systems have the ability of physical integration. This means that different communications (e.g. WAMS, SCADA or SPMS) can use the same transmission media and the same routers. In this environment, communication of different applications (e.g. SCADA and SPMS) can virtually be implemented such that communication limitation of each of

Wide Area Measurement Systems (WAMS) is a new opportunity for system operators to monitor, operate, control and protect power systems in wide geographical area. The WAMS combines the data provided by synchrophasor and conventional measurements with the capability of new communication systems in order to obtain dynamic information of the

Fiber High Low High Power Line Medium Low High Leased Line Medium Low-Medium High

WPAN Low-Medium Low-Medium Low WLAN Low-Medium Medium Low WMAN Medium Medium Low WWAN Low-Medium High Low

Protection System) should not be implemented under WWAN technologies.

their provided bandwidth, latency and security. This is shown in Table 1.

well-known LEO satellites.

hours to circle the earth.

Guided

Unguided

them is satisfied.

**7. Conclusion** 

**6.3 Comparison of transmission media** 

Wireless

Table 1. Transmission Media Comparison (Shahraeini et al., 2010).

**MBWA**: Mobile broadband wireless access (MBWA), which is standardized under the name IEEE 802.20, creates mobile metropolitan networks with a speed up to 250 kilometers per hour. It uses licensed frequency band below 3.5 GHz and allows maximal data rates of 1 Mbps for downlink and 300 Kbps for uplink. The maximum range of the cells is 2.5 km. Because of short latency in MBWA technology, this technology is a good choice for mobility data and it can be compared with 3G mobile networks, which focus on the voice (Fourty et al., 2005; Shahraeini et al., 2010).

**GPRS**: General Packet Radio Service (GPRS or sometimes called 2.5G) is a packet data bearer service for wireless communication over GSM (Global System for Mobile). It applies a packet radio principle to transfer user data packets efficiently between mobile stations and external IP networks. GPRS allows IP-based applications to run on a GSM network (Shahraeini et al., 2010). Using unused channels in the GSM network, it provides moderate speed data transfer. The data speeds can range from 9.6 kbps (using one radio time slot) to 115 kbps (which can be achieved by merging 8 time slots) (Vaishnav et al., 2008).

**GSM**: It is the most popular second generation standard for mobile telephony systems in the world. There are some differences between GSM and GPRS. GSM is based on circuitswitching technology whereas GPRS makes packet switching network over GSM. GPRS bandwidth is higher than GSM; thus, GPRS has higher data speed toward GSM. In packet switching networks, the bandwidth is used only when a device transmits data. Conversely, connections are "always on" in circuit switching networks. Therefore, GPRS network charges are lower than GSM networks since the billing method is based on data volume and not on call time (Vaishnav et al., 2008).

**CDMA**: Code Division Multi-Access (CDMA) is another data networking technology for mobile communications. It allows all the users to utilize the entire frequency spectrum for all the time. Multiple simultaneous transmissions are separated by using coding theory. Only users associated with a particular code can understand each other. CDMA can create 64 logical channels whereas 8 channels are available in GPRS (Vaishnav et al., 2008).

**3G mobile Carrier services**: 3rd Generation networks provide new data carrier services for mobile users. For instance, some networks support High Speed Packet Access (HSPA) data communication with HSDPA standard to provide improved downlink speeds. Furthermore, HSUPA standard is used for uplink speed enhancement. HSDPA provides downlink data rates up to 14.4 Mbps and uplink data rates 384 Kbps. HSUPA provides improved upload data rates of up to 5.76 Mbps (Shahraeini et al., 2010). Another 3G standard for data communication, CDMA2000, allows a maximum theoretical data rate of 2 Mbps (Fourty et al., 2005).

#### **6.2.4 Wireless Wide Area Network (WWAN)**

Satellite communications may be used either when a guided media cannot be established between a remote site and the control center or when there is no line-of-sight between such a remote site and pre-installed communication network. Satellites, according to their orbits, may be classified as geostationary, medium, or low earth orbit satellites described below (Fourty et al., 2005):

**Geostationary Earth Orbit (GEO)** satellites are at an altitude of 35786 kilometers above the equator. GEO rotate around the earth at the same speed of earth rotation; thus, they appear to be fixed from the surface of the earth.

**MBWA**: Mobile broadband wireless access (MBWA), which is standardized under the name IEEE 802.20, creates mobile metropolitan networks with a speed up to 250 kilometers per hour. It uses licensed frequency band below 3.5 GHz and allows maximal data rates of 1 Mbps for downlink and 300 Kbps for uplink. The maximum range of the cells is 2.5 km. Because of short latency in MBWA technology, this technology is a good choice for mobility data and it can be compared with 3G mobile networks, which focus on the voice (Fourty et

**GPRS**: General Packet Radio Service (GPRS or sometimes called 2.5G) is a packet data bearer service for wireless communication over GSM (Global System for Mobile). It applies a packet radio principle to transfer user data packets efficiently between mobile stations and external IP networks. GPRS allows IP-based applications to run on a GSM network (Shahraeini et al., 2010). Using unused channels in the GSM network, it provides moderate speed data transfer. The data speeds can range from 9.6 kbps (using one radio time slot) to

**GSM**: It is the most popular second generation standard for mobile telephony systems in the world. There are some differences between GSM and GPRS. GSM is based on circuitswitching technology whereas GPRS makes packet switching network over GSM. GPRS bandwidth is higher than GSM; thus, GPRS has higher data speed toward GSM. In packet switching networks, the bandwidth is used only when a device transmits data. Conversely, connections are "always on" in circuit switching networks. Therefore, GPRS network charges are lower than GSM networks since the billing method is based on data volume and

**CDMA**: Code Division Multi-Access (CDMA) is another data networking technology for mobile communications. It allows all the users to utilize the entire frequency spectrum for all the time. Multiple simultaneous transmissions are separated by using coding theory. Only users associated with a particular code can understand each other. CDMA can create

**3G mobile Carrier services**: 3rd Generation networks provide new data carrier services for mobile users. For instance, some networks support High Speed Packet Access (HSPA) data communication with HSDPA standard to provide improved downlink speeds. Furthermore, HSUPA standard is used for uplink speed enhancement. HSDPA provides downlink data rates up to 14.4 Mbps and uplink data rates 384 Kbps. HSUPA provides improved upload data rates of up to 5.76 Mbps (Shahraeini et al., 2010). Another 3G standard for data communication, CDMA2000, allows a maximum theoretical data rate of 2 Mbps (Fourty et

Satellite communications may be used either when a guided media cannot be established between a remote site and the control center or when there is no line-of-sight between such a remote site and pre-installed communication network. Satellites, according to their orbits, may be classified as geostationary, medium, or low earth orbit satellites described below

**Geostationary Earth Orbit (GEO)** satellites are at an altitude of 35786 kilometers above the equator. GEO rotate around the earth at the same speed of earth rotation; thus, they appear

64 logical channels whereas 8 channels are available in GPRS (Vaishnav et al., 2008).

115 kbps (which can be achieved by merging 8 time slots) (Vaishnav et al., 2008).

al., 2005; Shahraeini et al., 2010).

not on call time (Vaishnav et al., 2008).

**6.2.4 Wireless Wide Area Network (WWAN)** 

to be fixed from the surface of the earth.

al., 2005).

(Fourty et al., 2005):

**Low Earth Orbit (LEO)** satellites rotate between 750 and 1500 kilometers orbit. LEO satellites are widely used for communications. Iridium, Globalstar and Orbcomm are some well-known LEO satellites.

**Medium Earth Orbit (MEO)** satellites are at altitudes between nearly 10,000 and 20,000 kilometers. From the view point of the earth, MEO rotate slowly in longitude; feel like 6 hours to circle the earth.

These three types of satellites cover surface of the earth almost everywhere, hence; WWAN technologies provide remote sites connections. Although satellites can connect remote sites to the control center, high latency of these connections may create serious problems for some WAMS applications. As a result of this, some critical applications such as WAPS (Wide Area Protection System) should not be implemented under WWAN technologies.
