Wireless Personal Communications: What Is It?

Donald C. Cox

One-line summary: Wireless PCS is in a chaotic and transitionary state; it will evolve into two main classes - "high-tier" systems that focus on highly mobile voice communications, and "low-tier" systems that minimize cost, maximize the number of users per cell, and provide voice and data capability.

Overview/Main Points

Classes of PCS: Messaging (voice mail, fax, e-mail), paging (broadcast with no return channel), real-time two-way communications, and "agents& represent broad classes of PCS. These classes should work across different geographical scales, with varying QOS.
Digital cordless: CT-2, DECT - 32kb/s ADPCM, 10-50ms RTT, 4QAM modulation, time-division duplex are the common features of these standards.
High-tier PCS: high-tier PCS is the catch-phrase for early digital cellular systems such as IS-54, IS-95, GSM, and DCS-1800. Such systems are characterized by complex modulation and speech coding techniques and large macro-cells on the order of 0.5-3.0 kilometers, with the goal of maximizing both users/MHz and users per cell, implying high power consumption, network complexity, and end-end latency.
Wide-area data: ARDIS, CDPD, RAM, and now Metricom are examples of commercialized technologies. Typically such services exhibit high mobility, low data throughput, and high latencies. In the face of low-tier PCS, the future of such services is uncertain.
WLAN: Very desirable properties, but currently unprofitable in spite of severe commercial competition. Two main designs include centralized coordination and ad-hoc self-organizing LANs.
Low-Tier PCS: Evolutionary trends are towards microcell coverage for frequency reuse and low-power benefits, overlay networks of LAN, MAN, and WAN wireless systems, low-complexity coding and efficienct modulation, and FDMA or CDMA to relax time synchronization requirements.

Relevance

This paper gives describes the current state of wireless communications and speculates on the future, from a telecommunications perspective. The evolutionary trends presented are strongly argued and supported with evidence, and the facts described are accurate without being overly detailed.

Flaws

Nearly all systems or other high-level issues involved with wireless communications are totally ignored.
The future demand for high-speed data services that exhibit high mobility seems to be underestimated; wireless voice and paging services are overemphasized. (This is probably because the author is a telephone engineer.)
Much speculation is stated as fact rather than possibility.

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