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.The packet data communications capabilities definedin the PACS standards, together with the ability to aggregatemultiple 32-kbps channels, make it possible for users to accessthe Internet from their PCs equipped with suitable wirelessmodems at speeds of up to 200 kbps.When using the packetmode of PACS for Internet traffic, radio channels are not dedi-cated to users while they are on active Internet sessions, whichcan be very long.Rather, radio resources are used only whendata are actually being sent or received, resulting in very effi-cient operation and minimally impacting the capacity of thePACS network to support voice communications.PACS was designed to support the full range of advancedintelligent network (AIN) services, including custom callingfeatures and personal mobility.As new AIN features aredeveloped, the PACS-compliant technology will evolve tofacilitate incorporation of the new services.SummaryThe market for PCS is very competitive.Already PCS isexerting downward price pressure on traditional analog cel-lular services where the two compete side by side.PACSenables PCS operators to differentiate their offeringsthrough digital voice clarity, high-bit-rate data communica-tions, and advanced intelligent network services all in alightweight handset.Moreover, the cost savings and ease ofuse associated with PACS make it very economical for resi-dential and business environments compared to competitivehigh-powered wide area systems.See alsoPersonal Handyphone SystemPersonal Communication ServicesVoice CompressionWireless Communications Services 254 PERSONAL AIR COMMUNICATIONS TECHNOLOGYPERSONAL AIR COMMUNICATIONSPERSONAL AIR COMMUNICATIONSTECHNOLOGYTECHNOLOGYPersonal Air Communications Technology (pACT) is a wire-less two-way messaging and paging technology that isoffered as an alternative to wireless Internet Protocol (IP),also known as Cellular Digital Packet Data (CDPD).The pACT specification, released in 1995, was developed toenable compact, inexpensive devices to access low-cost, high-capacity network infrastructures.The protocol enhancesone-way paging, response paging, two-way paging, voicepaging, telemetry, and two-way messaging applications.ThepACT protocol thus addresses the demands of a growingmarket for narrowband PCS.Despite huge investments inspectrum for narrowband PCS, some U.S.paging carriersare already running short of bandwidth.This situation hasprompted them to look for ways to add capacity to their net-works.In major U.S.cities, the solution has been to makebetter use of existing spectrum.pACT supports two-way messaging and paging applica-tions while still retaining all the strengths of one-way pag-ing services, including long battery life, good in-buildingreception, and ubiquitous coverage.pACT also provides car-riers with the ability to substantially increase system capac-ity by more efficiently utilizing spectrum, thereby allowingfor more cost-effective paging and messaging services.Itscellular-like network design enables carriers to take advan-tage of capacity gains through frequency reuse, a funda-mental difference from other two-way systems.The difference between wireless IP and pACT is that theformer is TCP/IP-centric, whereas the latter is UserDatagram Protocol/Internet Protocol (UDP/IP) centric.Whilewireless IP compresses the standard 40-byte TCP/IP headerto an average of 3 bytes to conserve bandwidth, pACT com-presses the header to only 1 byte.The greater compression isimportant for providing a short alphanumeric messaging ser-vice, especially when the message body is roughly the same PERSONAL AIR COMMUNICATIONS TECHNOLOGY 255size as the header.Consequently, the maximum number ofsubscribers that can be supported by the system is con-strained not by protocol efficiency but by service traffic.ApplicationsTwo-way wireless messaging is working its way into a myriadof user applications where one-way messaging is no longeradequate.These are applications where time is of the essence,and guaranteed message delivery is critical.pACT uses thesame upper layers of the protocol stack as wireless IP, makingit suitable for a broad range of messaging applications, includ-ing two-way-paging, e-mail, fleet dispatch, telemetry, transac-tion processing (e.g [ Pobierz całość w formacie PDF ]
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.The packet data communications capabilities definedin the PACS standards, together with the ability to aggregatemultiple 32-kbps channels, make it possible for users to accessthe Internet from their PCs equipped with suitable wirelessmodems at speeds of up to 200 kbps.When using the packetmode of PACS for Internet traffic, radio channels are not dedi-cated to users while they are on active Internet sessions, whichcan be very long.Rather, radio resources are used only whendata are actually being sent or received, resulting in very effi-cient operation and minimally impacting the capacity of thePACS network to support voice communications.PACS was designed to support the full range of advancedintelligent network (AIN) services, including custom callingfeatures and personal mobility.As new AIN features aredeveloped, the PACS-compliant technology will evolve tofacilitate incorporation of the new services.SummaryThe market for PCS is very competitive.Already PCS isexerting downward price pressure on traditional analog cel-lular services where the two compete side by side.PACSenables PCS operators to differentiate their offeringsthrough digital voice clarity, high-bit-rate data communica-tions, and advanced intelligent network services all in alightweight handset.Moreover, the cost savings and ease ofuse associated with PACS make it very economical for resi-dential and business environments compared to competitivehigh-powered wide area systems.See alsoPersonal Handyphone SystemPersonal Communication ServicesVoice CompressionWireless Communications Services 254 PERSONAL AIR COMMUNICATIONS TECHNOLOGYPERSONAL AIR COMMUNICATIONSPERSONAL AIR COMMUNICATIONSTECHNOLOGYTECHNOLOGYPersonal Air Communications Technology (pACT) is a wire-less two-way messaging and paging technology that isoffered as an alternative to wireless Internet Protocol (IP),also known as Cellular Digital Packet Data (CDPD).The pACT specification, released in 1995, was developed toenable compact, inexpensive devices to access low-cost, high-capacity network infrastructures.The protocol enhancesone-way paging, response paging, two-way paging, voicepaging, telemetry, and two-way messaging applications.ThepACT protocol thus addresses the demands of a growingmarket for narrowband PCS.Despite huge investments inspectrum for narrowband PCS, some U.S.paging carriersare already running short of bandwidth.This situation hasprompted them to look for ways to add capacity to their net-works.In major U.S.cities, the solution has been to makebetter use of existing spectrum.pACT supports two-way messaging and paging applica-tions while still retaining all the strengths of one-way pag-ing services, including long battery life, good in-buildingreception, and ubiquitous coverage.pACT also provides car-riers with the ability to substantially increase system capac-ity by more efficiently utilizing spectrum, thereby allowingfor more cost-effective paging and messaging services.Itscellular-like network design enables carriers to take advan-tage of capacity gains through frequency reuse, a funda-mental difference from other two-way systems.The difference between wireless IP and pACT is that theformer is TCP/IP-centric, whereas the latter is UserDatagram Protocol/Internet Protocol (UDP/IP) centric.Whilewireless IP compresses the standard 40-byte TCP/IP headerto an average of 3 bytes to conserve bandwidth, pACT com-presses the header to only 1 byte.The greater compression isimportant for providing a short alphanumeric messaging ser-vice, especially when the message body is roughly the same PERSONAL AIR COMMUNICATIONS TECHNOLOGY 255size as the header.Consequently, the maximum number ofsubscribers that can be supported by the system is con-strained not by protocol efficiency but by service traffic.ApplicationsTwo-way wireless messaging is working its way into a myriadof user applications where one-way messaging is no longeradequate.These are applications where time is of the essence,and guaranteed message delivery is critical.pACT uses thesame upper layers of the protocol stack as wireless IP, makingit suitable for a broad range of messaging applications, includ-ing two-way-paging, e-mail, fleet dispatch, telemetry, transac-tion processing (e.g [ Pobierz całość w formacie PDF ]