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> Tescom tc-3010A, TC3010A CT2 tester
Tescom tc-3010A, TC3010A CT2 tester
Provides testing for the CT2 Telepoint Standard
The CT2 spectrum allocation consists of 40 FDMA channels with 100-kHz spacing in the range 864-868 MHz. The 100-kHz spacing reduces the bandwidth efficiency to half its value for CT1 (50 kHz per duplex channel). The maximum transmit power is 10 mW, and two-level power control helps to prevent the desensitization of base station receivers, and as a by-product, contributes to improved frequency reuse. A call re-establishment procedure on another carrier after three seconds of handshake failure gives robustness against the usual impairments of radio channels. The control data bits are protected against errors.
CT2 also supports the transmission of data, up to 2.4 kb/s through the speech codec (4.8 kb/s with an increased error rate), and higher rates by accessing the 32 kb/s bearer channel directly.
The most salient features of that standard are the digital transmission format and the use of time division duplexing (TDD). With CT2, speech is first digitized using a 32 kb/s adaptive differential pulse code modulation (ADPCM) encoder (CCITT G.721). The time-compressed digitized speech and control data are modulated onto a carrier at a rate of 72 kb/s using Gaussian filtered FSK (GFSK) and are transmitted in 2-ms frames. Each frame includes one base-to-handset and one handset-to-base burst (Fig. 1). This mode of duplexing (TDD) has significant advantages: the expensive duplex filter required with frequency duplexing is replaced by a switch; both transmission and reception antenna diversity can be used (due to propagation path reciprocity); and rather arbitrary frequency bands can be allocated.
CT2 was promoted as a Telepoint standard. Telepoint networks use cordless base stations to provide wireless pay phone services. Incoming calls are not supported with the basic service. They require additional functionality such as manual registration and paging. User acceptance of CT2-Telepoint varies widely over the continents. No breakthrough was achieved in Europe; in the United Kingdom, for example, the last operator terminated service in 1993. In Hong Kong, however, there are 150 000 subscribers to CT2 Telepoint service, and systems are being deployed in other parts of Southeast Asia, including China, Malaysia, Singapore, and Thailand. European sales of CT2 handsets for 1994 are estimated to be 0.4 million, with projected increases to 0.5 and 0.6 million in 1995 and 1996, respectively. The current embedded base is estimated at 0.6 million units.
A Canadian enhancement of the CT2 CAI, called CT2+, is designed to provide some of the missing mobility management functions. For that purpose, 5 of the 40 carriers are reserved for signaling. Each carrier provides 12 Common Signaling Channels (CSC) using TDMA. These channels support location registration, location updating, and paging, thereby enabling the Telepoint subscriber to receive calls. CT2+ operates in the frequency band 944-948 MHz.
In summary, the family of CT2 standards is an attractive option for cordless and Telepoint systems optimized with respect to cost.
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