The Repeater for WCDMA Cellular Mobile Systems

He Songbai, Wang Bin, You Fei, Yan Xiaohuan, Bao Jingfu School of Electronic Engineering, University ofElectronic Science and Technology, Chengdu 610054, China E-mail: [email protected] Abstract-This paper presents the principles and constitutions of mountains or lofty buildings, areas with no significant RF and fiber optic repeaters to provide wideband code division increase of speech volume, but increase of activity radius of multiple access(WCDMA) mobile communication services to users and areas with high call drop rate, low handover success previous blind areas such as places far away from the city, vast rate, poor coverage effect, low connection rate, or poor call and sparsely populated, inside the buildings or in the effect. underground mall. The thermal noise generated by the repeater increases the uplink noise level and degrades the uplink capacity The main components of a repeater are uplink and downlink of a BS(Base Station). In this paper, we analyze the noise floor transceivers, management module and power supply module. increase and capacity degradation, as well as propose to select For different ways of application, there are different kinds of the operation carrier frequency and fix the channel bandwidth to repeaters such as RF wideband repeater, fiber optic repeater 5MHz by using a surface acoustic wave(SAW) filter to degrade and band selective repeater, et.. The main specifications of the noise floor in the WCDMA repeater. Finally, it gives some evaluating a repeater are its intelligence (i.e. local and remote experiment results, and the developed repeater has been used for monitor), Adjacent Channel Power Ratio(ACPR), noise figure the WCDMA mobile communication networks in the Hangzhou and reliability. and Suzhou telecom. of China telecom.. However, when used in network optimization, a problem occurs in current repeaters[5]. The limit of output noise floor of I. INTRODUCTION the uplink leads to closure of the base station, which makes it As an engineering technology to solve the problem of blind impossible to accomplish the communication. areas and enhance the network coverage, repeater plays an In this paper, design of RF intelligent repeater and fiber important part in present GSM and CDMA mobile optic repeater is proposed, as well as the solution to closure of communication business network0l]. With granting of the the base station resulting from noise level of the repeater WCDMA license in China and large-scale construction of uplink. The test result of repeater for WCDMA cellular mobile WCDMA mobile communication network, the repeater telecommunication systems, which is researched by the (especially RF repeater), by right of its convenient installation authors' group, is also included. and low cost(which is only about 20% cost of that of the base station), will inevitably be widely used in the WCDMA II. THE PERFORMANCE OF WCDMA COVERAGE SYSTEM mobile communication systems. It is applicable not only in the When a repeater is located in a cell, the model of WCDMA initial network construction stage, but also in network quickly coverage system is shown in Fig.2, the BS equipment in the developing and optimizing stagel14]1 The repeater in network system receives output noise from the repeater. It can be seen application is shown in Fig. 1. that because the gain of repeater is usually big, uplink noise 1SLk seie floor of the repeater will possibly exceed reception sensitivity antenna antenna of the base station and thus results in closure of the base hik ternne antenia anLtena BS Repeater MS r

LS1 LS2 Fig. 1 The scheme of RF intelligent repeater in network optimization

This system is applicable for areas and zones as follows: Fig.2 The model of WCDMA coverage system areas far away from the city, vast and sparsely populated areas, wide plain zones, areas where repeaters fail to solve matters station, so communication is not able to be carried through. concerning antenna isolation, directional coverage to zonal Furthermore, as the repeater brings noise, system capacity will areas such as expressways and railways, weak zones or dead be reduced. zones caused by complex landforms, land features, high

0-7803-9584-0/06/$20.00O2006 IEEE. 2511 A. Relationship between noise level of BS from repeaters and the gain and bandwidth of repeater uplink The generated noise power inside the repeater uplink can be written as: PNR = KTBFG (1)

Where K is Boltzmann constant= 1.38 x 10 23J / K, T is absolute temperature in kelvins(K), B is bandwidth, F is the noise figure of repeater uplink, and G is the gain ofrepeater uplink. Fig.3 The block diagram of RF band selective repeater Take the design of fiber optic repeater as an example. Let -to-noise at the input port ofBS. When a repeater is used the downlink power ofthe fiber optic repeater PO= 43dBm and to extend cellular service, the BS in the coverage system someone makes a call by a in a place which has receives output noise from the repeater. The signal-to-noise -9OdBm reception power level. Assume sending power ofthe S'IN' at the input port of BS becomes worse. In this case, the mobile phone is 2W. Now let us analyze noise level ofBS capacity ofthe BS is given by from the repeater. C =Blog2(1+ S /,) (6) Solution: N a. Space loss between the repeater and the mobile phone Thus L,2 is C -

2512 At the remote site, another E/O module is mounted, which Fig.5 shows the exterior ofthe developed repeater. The picks up the link signal into the remote unit. The signal is equipment is supplied by 220V AC and includes the RF connector, remote control interface.

ter Sleseice axLtenL Fig.6 shows the downlink adjacent channel power ratio (ACPR). The ACPR satisfied at less -45dBc, which is the f3ber: required specification described in the 3GPP TS25.104. The measured noise figure ofthe uplink is listed in Table.1. Simultaneously, Table.1 gives the required RF specifications MwEater SlaLveS for the proposed repeaters. Table.1 The main technical specification of developed Fig.4 The block diagram of fiber optic repeater repeaters shifted back to the original frequency and retransmitted on the Frequency bands 1920MHz - 1980MHz Up-link service antenna. Using the fiber optic repeater, the antenna 211 OMHz - 2170MHz Down-link isolation at the remote site has to be 75 dB, regardless of the gain set in the repeater.. Duplex spacing 190MHz Signal from MS received by remote unit is coupled from Channel bandwidth 5MHz local unit to BS through contrary process. Maximum average 3OdBm,33dBm,4OdBm ,Down-link output power (one 30dBm , Up-link, WCDMA test V. EXPERIMENT RESULTS channel) mode 1. Noise figure at < 3.5dB Up-link maximum gain < 3.5dB Down-link ACPR -47dBc (±5MHz -55dBc @±IOMHz Frequency error 20Hz Gain control 30dB/ldB range/step ALC When it is in Max output power, output power will keep within 2dB fluctuate or turn off if input power increase lOdB Local management USB or RJ45 interface Fig. 5 Exterior of developed repeater Remote management GSM/GPRS interface RF connectors BNC Operating temperature -30 up to 50°C Power supply 90-23OVac

VI. CONCLUSION The novel RF and fiber optic repeaters with choosing operation carrier frequency and using SAW filter to reduce the uplink noise level of the BS are developed for WCDMA mobile communication systems. The paper presents the WCDMA mobile communication systems coverage solutions and coverage systems model. It analyzes the uplink of the repeater noise floor, and then proposes a scheme to reduce the Fig.6 Characteristics of downlink ACPR systems noise level. The radio characteristics of the developed

2513 repeaters satisfy the required specifications in the 3GPP TS25. 101, TS25.106 and TS25.104 specifications.

ACKNOWLEDGMENT This project is supported by UESTC-VARA laboratory.

REFERENCES [1] Zu Huahong, et.al, RF Engineering of Cellular mobile communication, Pos and telecom press, 2005. [2] Ramjee Parsad Werner Mohr Walter Konhauser, Third Generation Mobile Communication Systems, Artech House. [3] 3GPP TS25.106 UTRA repeater radio transimission and reception. www.tekotelecom.it r41r5i Yasushi ITO, et al., "Novel Repeater with Automatic Gain Control for Indoor Area", 20 5 Asia-Pacific Conference Proceedings, p'2963-2965, Dec.2005. [6] Cotter W.Sayre, Complete Wireless Design, The McGraw- Hill Companies, Inc.

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