Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1999-09-21
2001-07-31
Ghebretinsae, Temesghen (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C370S335000
Reexamination Certificate
active
06269113
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 arising from an application entitled, MODULATED SIGNAL GENERATOR FOR WIDEBAND CDMA WLL SYSTEM, earlier filed in the Korean Industrial Property Office on Sep. 21, 1998, and there duly assigned Ser. No. 1998-039045.
1. Field of the Invention
The present invention relates to a modulated signal generator for a wideband code division multiple access (CDMA) system used in a wireless local loop (WLL) system. More particularly, the present invention relates to a modulated signal generator for testing the performance of an amplifier and a demodulator in the WLL-CDMA system having a 2.3 GHz wide bandwidth.
2. Description of the Related Art
The CDMA system modulates signals from each user with each user's own intrinsic code, prior to transmission, and then spreads them to each cells. In CDMA system, the same frequencies are used in all cells. In order to retrieve the signals, a reverse spreading of the received signals is performed, and then the despreaded signals are multiplied by the same code used during the transmission. As such, the CDMA is effective in decoding the transmission signals in the presence of high interference along the propagation paths.
In the CDMA system, a channel from a base station (BS) to a radio terminal (RT) is known as a forward link, and a channel from a RT to a BS is known as a reverse link.
In the CDMA system, a channel spacing of 5 MHz is used. A convolutional encoder is used to lower the transmission bit error, and the othogonal codes are assigned to each channel intrinsically for the forward link distinction. However, in wideband CDMA system, a direct sequence spreading is used at a chip rate of 4.096 Mcps (Mega chip per second). Each channel is modulated using the technique known as a binary phase shift keying (BPSK) modulation and a quadrature phase shift keying (QPSK) modulation. Moreover, the channel spacing may be spread at a higher spreading rate.
The wideband CDMA channels are classified into a power control and signaling (PCS) channel and a traffic channel. The PCS channel includes a reverse/forward pilot channel and a signaling channel. The traffic channel includes an access channel, a synchronous channel, a paging channel, and a traffic channel for transmitting the real data traffic.
The modulation channel in the base station includes a pilot channel, a synchronous channel, paging channel, traffic channel, and a PCS channel. Each channel of a base station includes a convolutional encoder, an interleaver, a symbol repeator, a serial-to-parallel converter, a signal band spreader, and a scrambler.
The modulation channel of a radio terminal includes an access channel and a traffic channel. The access channel is consists of an access pilot channel and an access information channel, and the traffic channel is consists of a pilot channel, a PCS channel and a traffic information channel. Each channel includes a convolutional encoder, an interleaver, a symbol repeater, a serial-to-parallel converter, and a signal-band spreader.
The channel structure adopting CDMA technology is disclosed in “CDMA Cellular Mobile Communication and Network Security”, Chapter 9,10: Prentice Hall PTR, 1997.
In the modulator of a wideband CDMA system as described in the above, the spectrum/output signal characteristics depends on the spread code patterns and the structure of a modulation-signal generator. When a RF amplifier amplifies the analog signal in a transmitter (BS or RT), the performance of a RF amplifier or decoder depends on the modulation process. Thus, the modulated signals by a wideband CDMA system needs to be examined to evaluate whether the performance of the amplifier/decoder in a wideband CDMA system is working properly.
In the prior CDMA system, in order to test the characteristics of the sidelobe regrowth of a RF amplifier, noise signals were used. Although the noise signals exhibit similar spectrum characteristics to that of the CDMA signals, the bandwidth is limited to test a wide range of bandwidth. Moreover, it is impossible to model the real CDMA signals accurately the noise signals, and further, the noise signals could not be used in testing the performance of a demodulator.
A base station or radio terminal using wideband CDMA technology includes a plurality of channels, and the digital gain, the data transfer rate, and the spread coding technique varies depending on the different standards. Thus, the current testing apparatus could not generate such a wideband CDMA testing signals responsive to different testing conditions in order to properly test the working functions of wideband CDMA system.
SUMMARY OF THE INVENTION
One of the objects of the present invention is to provide a modulated-signal generator to test the working functions of a wireless local loop (WLL) CDMA system.
Another object of the present invention is to provide a modulated signal generator for the WLL CDMA system, which can set a signal resource to be modulated per each channel at a specific data transfer rate, digital gain, reference clock, spread code, and spread operation mode designated by the operator.
REFERENCES:
patent: 5511073 (1996-04-01), Padovani et al.
patent: 5751705 (1998-05-01), Sato
patent: 5751761 (1998-05-01), Gilhousen
patent: 6097715 (2000-08-01), Ichihara
Cha Steve
Ghebretinsae Temesghen
Klauber & Jackson
Samsung Electronics Co,. Ltd.
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