Anthony R. Noerpel

PACS: Personal Access Communications System-a tutorial

The Personal Access Communications System (PACS) is an American National Standards Institute common air interface standard developed for the 1.9 GHz PCS band in the United States. PACS uses frequency division duplexing technology and is optimized to support low-mobility pedestrian outdoor usage and wireless local loop applications in a medium-range environment. PACS-Unlicensed B (PACS-UB) is a version of PACS using time division duplexing. PACS-UB has been optimized for private, indoor wireless PBX applications and cordless telephony. Both modes of operation are supported using the same portable hardware and the same signaling protocol.

Handover arrangement for a PCS network

A handover is required in wireless personal communications systems when a portable moves from one base station coverage area to another during the course of a conversation. In general, the handover should be completed while the portable is in the overlap region to be successful. This article considers several issues for handover management, handover detection, channel assignment, and radio link transfer.

Analyzing the trade off between implementation costs and performance: PCS Channel Assignment Strategies for Hand-off and Initial Access

YI-BING LIN, SESHADRI MOHAN, AND ANTHONY NOERPEL ersonal communications is expected to provide low-power/high-quality wireless access to the public switched telephone network (PSTN) [4,5]. The service area of a network providing personal communications services (PCS) is populated with a large number of ports, with each port providing coverage in its vicinity. Each port is assigned a group of channels (time slots, frequencies, spreading codes, or a combination of these) that can be either fixed or dynamic. This article assumes a fixed or quasi-static channel assignment [9]. The results may be extensible to dynamic channel assignment schemes [lo]. When a subscriber wishes to make or receive a phone call, the portable attempts to seize an available traffic channel for the call. For some PCS radio systems, the portable launches an access request on a common signaling channel and is then directed to a traffic channel (CT-2 Plus [14]). In other PCS radio systems the access attempt can be made directly on an available traffic channel (DECT [8], or Bellcore WACS [l]’). Owing to the limited number of servers or transceivers in a port, when a port is blocked there is no idle transceiver for the signaling channel. There is usually no provision (either no channel or no protocol, or both) for a portable to signal the need for a traffic channel to a blocked port and therefore access attempts cannot be queued by the network. If there is no available traffic channel or common signaling channel, the call is blocked. (An exception to this is the WACS system, which reserves a time slot channel called the system broadcast channel.) If there is an available traffic channel it is used for the call. The channel is released eitherwhen the call iscompleted or the portable (or the PCS subscriber) moves out of the coverage area. When a user moves from one coverage area to another while a call is in progress, a hand-off to the new port is required to maintain continuity and quality of the call. If the new port does not have an idle channel, the call may be dropped o r forced terminated. The forced termination probability is an important criterion in the performance evaluation of a PCS network. Forced termination of an ongoing call is considered less desirable than blocking of a new call attempt. Radio tech-

Performance of personal access communications system-unlicensed B

The FCC has allocated the band between 1920 MHz and 1930 MHz for unlicensed personal communications services (UPCS) using isochronous or circuit operation. The UPCS spectrum is between the licensed PCS spectrum bands of 1850-1910 MHz and 1930-1990 MHz. Terminal interoperability in both the UPCS spectrum on private indoor wireless systems and the licensed spectrum on public PCS systems is desirable and encouraged by the FCC. This paper presents a port channel assignment process for the personal access communications system-unlicensed B (PACS-UB) which abides by the FCC etiquette for UPCS and discusses the corresponding uplink and downlink performance. Uplink power control is employed to improve the uplink performance. PACS-UB has a high degree of commonality with licensed PACS to permit economical licensed/unlicensed terminals and common network services. The results of our simulation show that, at 1% to 2% blocking probability, 99% of downlink local-mean signal-to-noise plus interference ratio (SINR) values are above 17 dB for a 10 to 20 m port separation. For a three-dimensional office environment, the uplink limits the SINR performance, however, with uplink power control, a 5.5 to 7 dB improvement in the uplink SINR can be achieved even for high traffic load.

Integrated alerting and system broadcast channel for a wireless access system

A protocol is described which allows a wireless access system to dynamically multiplex the alerting, system information, and priority access request subchannels on its system-wide broadcast channel. These subchannels each have different requirements with respect to the message length and position within the framing structure; the described protocol meets each of their requirements. The protocol efficiently accommodates a wide range of alerting traffic levels and provides for efficient downloading of system information to subscriber units by using excess capacity when alerting traffic is low. It provides error detection capabilities above that provided by the radio channel alone and is easily extendible to accommodate other services such as paging and low bandwidth broadcast messaging. The flexibility provided by this protocol could permit a broad range of network architectures for wireless access.

Polling deregistration for unlicensed PCS

The FCC has allocated the spectrum between 1850-1910 and 1930-1990 MHz for licensed personal communications services (PCS) and the band between 1920-1930 MHz for unlicensed PCS (UPCS). This paper describes a polling deregistration protocol for a wireless access communications network which would support interoperability between licensed personal communications services (PCS) and unlicensed-PCS (UPCS). We show how the protocol can be efficiently implemented in the personal access communications system (PACS) for licensed PCS and in the PACS-Unlicensed Version B (PACS-UB). An analytical model is proposed to analyze the performance of the polling protocol. A cost function is derived, which can be used to estimate the optimal polling frequency.

PACS-UB, a protocol for the unlicensed spectrum

A set of radio air interface protocols is described which is intended to operate in the 1920 to 1930 MHz unlicensed PCS (UPCS) frequency band for isochronous operation, intended for voice and data circuit based communications. The Personal Access Communications System-Unlicensed B, or PACS-UB protocol is based on the PACS radio air interface protocol which is to operate in the licensed spectrum between 1850 and 1990 MHz. PACS-UB conforms to the new FCC Part 15, Subpart D, etiquette and is compliant with the rules of the FCC Memorandum Opinion and Order, June 9, 1994. PACS-UB could be used for wireless Centrex, or PBX applications as well as private residential applications. A dual-mode handset could provide private and public access using network intelligence to locate users.

Performance modeling of multitier PCS system

The emergence of multitier wireless access is being driven by the different compromises in technology required to provide wireless service in different environments. Three major tiers of wireless access are likely to emerge to providepersonal communications services (PCS): high-tier, low-tier, and unlicensed. Because of the service costs of the three tiers, the unlicensed system is given the highest priority to deliver the calls, and the high-tier system has the lowest priority to deliver the calls. To maintain this delivery priority, two multitier mobility management strategies have been proposed: the single registration strategy (SR) and the modified multiregistration strategy (MR). This paper proposes a new strategy called the lazy deregistration strategy (LDR) and compares the performance of the three strategies. We show that in most cases, LDR outperforms both SR and MR. The registration cost of SR is always no less than the cost of MR. The advantage of MR over SR is more significant if (i) when the user moves into the low-tier system, it is more likely that the currently visited low-tier VLR (visitor location register) is the same as the previously visited VLR, and (ii) the mobile station (MS) is more likely to move between the low-tier system and the high-tier system. The call delivery cost of MR is always no less than the cost of SR. The advantage of SR over MR is more significant if (i) the call arrival rate is large, (ii) the cost of delivering a call to the low-tier system is large, and (iii) the MS is likely to stay in the high-tier system.

Supporting PACS on a GSM MSC

The Personal Access Communications System (PACS) is one of the ANSI air interface standards developed for the 1.9 GHz PACS band in the U.S. It is a low-tier standard that has been optimized for both indoor wireless access and low mobility pedestrian outdoor usage. The Global System for Mobile Telecommunications (GSM) system is widely deployed in Europe and Asia and is being considered for many other regions around the world. A natural evolution path for PCS would be one that combined the advantages of the PACS with readily available GSM networking capabilities. This paper addresses solutions to interfacing a PACS radio system to a GSM or GSM derivative (PCS1900 or DCS 1800) network at the GSM A-interface.

Performance of PACS-UB for unlicensed operation

The FCC has allocated the band between 1920 MHz and 1930 MHz for unlicensed personal communications services (UPCS) using isochronous or circuit operation. The UPCS spectrum is between the licensed PCS spectrum bands of 1850-1910 kHz and 1930-1990 MHz. Terminal interoperability in both the UPCS spectrum on private indoor wireless systems and the licensed spectrum on public PCS systems is desirable and encouraged by the FCC. This paper presents a port channel assignment process for the Personal Access Communications System-Unlicensed B (PACS-UB) which abides by the FCC etiquette for UPCS and discusses the corresponding uplink and downlink performance. PACS-UB has a high degree of commonalty with licensed PACS to permit economical licensed/unlicensed terminals and common network services. The results of our simulation show that, at 1%-2% blocking probability, 99% of downlink local-mean SIR values are above 17 dB for 10 to 20 meters port separation. However, for a three dimensional office environment, the uplink limits the SINR performance.