Mobile Voice & Paging | Services

Mobile Voice

The most well known application for wireless communications is voice communications. Voice communication can be telephony; wide area (cellular), business location (wireless office) or home cordless (residential) or voice paging, dispatch (fleet coordination) or group voice (audio broadcasting). Service rates for voice applications typically involve an initial connection charge, basic monthly minimum fee, plus an airtime usage charge. When the customer uses service in another system than their home registered system, there may be a daily fee and/or a higher per minute usage fee.

Figure 1 shows that mobile telephone charges include recurring costs and usage costs. Mobile telephone systems also offer advanced features. In many cases, the advanced features are offered for free (e.g., voice mail) as they increase usage costs.

Figure 1: Mobile Telephone Costs

Paging

Paging services include tone paging, numeric paging, alpha (text) paging, and voice paging. Tone paging service notifies a paging customer that a message has been sent via a tone. This tone usually is designated to mean a callback to a single location is requested. The original “beep, beep” tone pagers that started it all have become very popular as entry-level private communications systems, including restaurants (beeping servers when orders are ready) and in other centralized locations where a tone page necessitates a choice in response to only one.

While the popularity of these types of pagers has decreased overall, some retailers continue to offer tone pagers as “loss leaders” allowing the publication of low prices in print ads to attract attention. Still, for dispatch operators or other industries that only need a response to a central office, tone pagers offer a cost-effective solution.

Numeric paging is the sending of paging messages, typically telephone numbers that are displayed on a small paging device. After the message is received, the user calls back the displayed telephone number to talk to the sender.

Figure 2 shows that the typical cost for numeric paging service typically involves signing up for local, regional, or nationwide coverage. Rate plans start with a monthly service charge that allows pages using a local telephone number. Additional charges may be assessed for 800 toll free and 0800 freephone access numbers. Paging carriers usually offer a maximum number of pages per month and pages that additional per-page charges may apply for pages that are sent beyond the pre-defined limit.

Figure 2: Paging Cost

Alpha paging displays numerical and textual information. This can take many forms, from verbatim text messages to weather reports. Messages can be recorded into voice mail where operators type them up and send them out, or callers can dictate messages to live operators directly. Many carriers bundle free news, weather and sports feeds from other sources. While some carriers offer unlimited numeric usage, many charge for additional pages (both numeric and text message) beyond a pre-defined limit. Some carriers charge so much per character while others simply charge by the message.

Voice pagers broadcast messages through a built-in speaker in the paging unit. Message volume settings can usually be set to loud, soft or private, through an earpiece.

Two-way pagers allow fully interactive capabilities, permitting users to respond to pages by sending an original or canned alphanumeric message. Additional hardware must be purchased (or leased). Customers can lease the paging device for about $15 per month or purchase it for around $399.00.

Wireless Local Loop (WLL)

Wireless local loop (WLL) service refers to the distribution of telephone service from the nearest telephone central office to individual customers via a wireless link. In some cases, it is referred to as “the last mile” in a telephone network. This term is a bit misleading, though, because the coverage area of a WLL system may extend many miles from the central office.

Competitive local exchange carriers (CLEC) are competitors to the incumbent local exchange carriers (ILECS) and are likely to use WLL systems to rapidly deploy competing systems. If CLECs do not use wireless systems, they must either pay the existing phone company for access to the local loop (resale) or dig and install their own wire to the local customers. Many countries, that do not have large wired networks such as the United States, are using wireless local loop as their primary phone system.

Figure 1 shows a wireless local loop system. In this diagram, a central office switch is connected via a fiberoptic cable to radio transmitters located in a residential neighborhoods. Each house that desires to have dial tone service from the WLL service provider has a radio receiver mounted outside with a dial tone converter box. The dial tone converter box changes the radio signal into the dial tone that can be used in standard telephone devices such as answering machines and fax machines. It is also possible for the customer to have one or more wireless (cordless) telephones to use in the house and to use around the residential area where the WLL transmitters are located.

Figure 1: Wireless Local Loop

The most basic service offered by wireless local loop (WLL) system is to provide standard dial tone service known as plain old telephone service (POTS). In addition to the basic services, WLL systems typically offer advanced features such as high-speed data, residential area cordless service, and in some cases, video services. To add value to WLL systems, WLL service providers will likely integrate and bundle standard phone service with other services such as cellular, paging, high speed Internet, or cable service.

WLL systems can provide for single or multiple-line units that connect to one or more standard telephones. The telephone interface devices may include battery back up for use during power outages. Most wireless local loop (WLL) systems provide for both voice and data services. The available data rates for WLL systems vary from 9.6 kbps to over several hundred kbps. WLL systems can be provided on cellular and PCS, private mobile radio, unlicensed cordless, and proprietary wideband systems that operate the 3.4 GHz range.

Wireless Cable (Wireless Networks)

Wireless Cable
Wireless Cable is the common term assigned to a radio frequency-based alternative to the cable TV distribution system. An example of wireless cable technologies is multichannel multipoint distribution system (MMDS) or local multichannel distribution system (LMDS). By 1998, there were over 10 million wireless customers throughout the world and over 1.1 million in the United States.

Wireless cable system can simultaneously supply local television channels and high-speed data services. MMDS has a high-speed standardized air interface allowing mass deployment of cable television service by the new unregulated telephone companies. Cable television providers, who have access to most homes, can now provide telephone service.

In 1996, some analog MMDS systems began upgrading to digital service. Through the use of digital video compression, digital transmission allows 5 or 6 times the video channel capacity. In addition to video programming, wireless cable can provide telephone service and data services.

Figure 1 shows that the major component of a wireless cable system is the head-end equipment. The head-end equipment is equivalent to a telephone central office. The head-end building has a satellite connection for cable channels and video players for video on demand. The head-end is linked to base stations (BS) which transmit radio frequency signals for reception. An antenna and receiver in the home converts the microwave radio signals into the standard television channels for use in the home. Like traditional cable systems a set-top box decodes the signal for input to the television. Low frequency wireless cable systems can reach up to approximately 70 miles.


Figure 1: Wireless Cable System
Wireless cable is one of the most economical technologies available for the delivery of pay television service. Wireless cable systems do not require extensive networks of cables and amplifiers, bringing the offered price generally lower than a traditional cable service. To the customer, a wireless cable system operates in the same manner as a traditional cable system. Because wireless signals are transmitted over the air rather than through underground or above-ground cable networks, wireless systems may be less susceptible to outages, offer better signal quality and be less expensive to operate and maintain than traditional cable systems. In conventional coaxial cable distribution networks, the television signal quality declines in strength as it travels along the cables and must be boosted by amplifiers thus introducing distortion into the television signal.

To add security for wireless cable systems, so unauthorized users do not gain access to the system (stealing service), signals from video sources are scrambled with a code. The user must have the code to successfully view the video signals. Like traditional cable systems, wireless cable systems employ “addressable” subscriber authorization technology, which enables the system operator to control centrally the programming available to each individual subscriber, such as a pay-per-view selection

There are two primary methods of providing a communication path back from the end customer to the network operator: a telephone line and wireless. Wireless cable systems have typically only provided wireless downlink service (radio transmission from the system to the customer). Some of the new wireless cable systems now dedicate some of their radio channel capacity to uplink channels (from the customer to the system). Uplink channels allow the customer to select programming sources (such as pay per view) or may allow two-way Internet access.

Wireless Piconets (Wireless Networks)

Wireless Piconets
Wireless piconets are very small networks that connect 5 to 10 devices or allow access to each other. Wireless piconets are primarily personal networks that allow accessories such as printers and headsets and other devices to interconnect without the need for wires. These communication systems allow for the connections to be dynamically added and removed between devices.

A particular form of wireless piconet is called Bluetooth. The Bluetooth system is an industry standard wireless data network. Information and the specifications for Bluetooth can be found at www.Bluetooth.com.

Figure 1 shows Bluetooth devices that have created temporary connections. In this diagram, the personal digital assistant (PDA) device is synchronizing (deleting, changing, and adding) addresses with a laptop computer. The laptop computer is also connected to the Internet through a Bluetooth enabled access node. A mobile phone is also synchronizing its phone book listing with the laptop computer. However, because it is out of direct range of communicating with the laptop, it communicates through the access node. The mobile phone is also communicating with a wireless headset.


Figure 1: Bluetooth Wireless Piconet

Residential Cordless (Wireless Networks)

Residential Cordless
Cordless systems are short-range wireless telephone systems that are primarily used in residential applications. Cordless telephones regularly use radio transmitters that have a maximum power level below 10 milliWatts (0.01 Watts). This limits their usable range to 100 meters or less.

The earliest generation of home cordless telephones used a single radio channel that used amplitude modulation. These first generation cordless phones were susceptible to electrical noise (static) from various types of electronic equipment such as florescent lights. The noise encountered when using these phones sometimes created a consumer impression that cordless telephone quality was below standard wired telephone quality. Improved versions of cordless phones that used FM modulation to overcome the electrical noise resulted. As cordless phones became more popular, interference from nearby phones became a problem. In apartment buildings where there were many users of cordless phones in close proximity, the ability to initiate and receive calls could be difficult as radio channels became busy with many users. This led to the development of cordless phones that used multiple radio channels. As voice privacy became more of an issue, cordless phones began to use scrambled voice. Some of these voice privacy systems were analog while a majority of cordless phones that offer voice privacy use digital transmission.

Figure 1 shows the evolution of cordless telephones. Until the mid 1990’s, most cordless telephones were limited to use in a small radio coverage area of their base station that was usually located in the home. That home base station was normally connected to the telephone line of the owner (either residential or a single office telephone line) and they were not intended to serve the general public. To add more value to the use of cordless phones, cordless telephones evolved to allow access to base stations in public locations. Cordless telephones could then be used in the home and in areas that were served by public base stations. The next evolution for cordless telephones was the combination of other types of wireless products and services into the cordless phone. This included the combination of wireless office and cellular telephones into a cordless phone.


Figure 1: Evolution of Cordless Telephone Systems
Most home cordless telephones used frequencies in unlicensed radio frequency bands. Because so many homes operate cordless phones, each manufacturer must build-in circuitry to minimize the interference caused by other cordless devices. The original cordless phones use a very crowded frequency band (around 27 and 49 MHz) utilizing analog radio wave modulation. Recently, cordless telephones have been developed that operate in the 902-928 MHz unlicensed industrial, scientific, and medical (ISM) frequency band.

Residential cordless telephones must automatically coordinate their radio channel access as they operate independently of any type of network control. To coordinate radio channel access and avoid interference to other cordless handsets installed in the vicinity, cordless phones perform radio channel scanning and interference detecting prior to transmitting a signal.

Because cordless telephone systems do not as a rule have a dedicated control channel to provide information, the cordless handset and base station continuously scan all of the available channels (typically 10 to 25 channels). Figure 2 shows the basic cordless telephone coordination process. This diagram shows that when the cordless phone or base station desires to transmit, the unit will choose an unused radio channel and begin to transmit a pilot tone or digital code with a unique identification code to indicate a request for service. The other cordless device (base station or cordless phone) will detect this request for service when it is scanning and its receiver will stop scanning and transmit an acknowledgement to the request for service. After both devices have communicated, conversation can begin. When another nearby base station detects the request for service, it will determine that the message is not intended for it and will not process the call and scanning will continue.


Figure 2: Cordless Telephone System

Wireless PBX | Telecommunications

Wireless PBX
Wireless PBX (wireless office) telephone systems are used in a business environment to provide similar features as a private branch exchange (PBX) with the ability of mobility throughout the office area. The wireless office commonly begins with a specialized wireless private branch exchange (WPBX) that has been adapted for wireless. While more complex than a home cordless telephone, it is not typically as complex as a complete cellular telephone system.

The WPBX telephone radio coverage area is usually within one or more company buildings or on a campus. The more popular WPBX systems use unlicensed frequencies with a protocol available only to the manufacturer of the WPBX. Ordinarily, WPBX telephones cannot be used outside the established campus.

These private WPBX systems use small wall mounted antennas, and like cellular, the space is divided to provide adequate capacity for the expected usage. WPBX telephones, like the one shown in Figure 1, have become commonplace in many hospitals and warehouse environments where the staff is primarily walking around to do their job.


Figure 1: Wireless Office Telephone System
Recent hybrids have been developed whereby the telephone handset has two technologies built into the operation of the phone. When the telephone is inside the WPBX coverage area (preferred) it acts as a private phone; when outside the WPBX coverage area, the phone has the ability to send and receive calls on the public cellular system, incurring airtime charges as any other cellular user.

Satellite (Wireless Networks)

Satellite
Satellite communication systems use of orbiting satellites to relay communications signals from one satellite station to one or several other users. Satellite communication can be divided into categories of fixed satellite service, positioning systems, and mobile satellite communication systems.

There are three basic types of satellite systems: geosynchronous earth orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO). GEO satellites hover at approximately 22,300 miles above the surface of the earth. GEO satellites revolve along with the earth once a day; they appear stationary with respect to the earth. The high-gain antennas used to receive signals from 22 thousand miles away (usually called “dish” antennas) are pointed directly toward the satellite. MEO satellites are located closer to the earth than GEO satellites and do not as a rule require high-gain antennas. This is important as MEO satellites revolve around the earth several times per day and fixed antennas cannot be used. The newest satellite technology being deployed is LEO satellites. LEO satellites are located approximately 450 miles above the surface of the earth. Because these satellites are relatively close to the earth, portable phones with smaller antennas can be used.

Figure 1 shows the different types of satellite communication systems. The GEO satellite system is primarily used for television broadcast services, as their satellites appear stationary above the Earth. MEO and LEO systems are used for mobile communications as they are located much closer to the Earth. However, these satellites continuously move relative to the surface of the Earth.


Figure 1: Satellite Systems
Mobile satellite telephone service allows customers to use specialized satellite mobile telephones to communicate in any part of the world to the PSTN through the use of communication satellites. Commercial communication satellite services began in the mid-1960’s with the establishment of Intelsat, a multinational organization with well over 130 member nations today. An organization known as the Communications Satellite Corporation (COMSAT) also was established in the early-1960’s and became the United States’ representative in Intelsat. These first commercial applications of satellites provided international telephone and television program transmission, primarily between the United States and Europe.