TECHNICAL PAPER Title:
UMTS Radio Interface System Planning and Optimization
Authors:
Esmael Dinan; Aleksey Kurochkin; Sam Kettani; Telecomm & Industrial
Date:
December 2002
Publication/Venue:
Bechtel Telecommunications Technical Journal Reprinted with permission
UMTS Radio Interface System Planning and Optimization Esmael Dinan
[email protected]
Aleksey Kurochkin
[email protected]
Sam Kettani
[email protected]
Issue Date: December 2002
INTRODUCTION
T
he goal of the UMTS (universal mobile telecommunications system) is to deliver multimedia services to the user in the mobile domain. UMTS and multimedia services have a significant impact not only on the RF (radio frequency) network, but also on the core network architecture. Care must be taken to allow current GSM (global system mobile) operators to protect their infrastructure investments when their networks are upgraded to support UMTS. The UMTS network architecture is depicted in . The core network handles call control and mobility man-
To PSTN
agement functionalities, while the UTRAN (UMTS terrestrial radio access network) manages the radio packet transmission and resource management. Packet routing and transfer within the core network are supported by definition of new logical network nodes called GGSN (gateway GPRS [general packet radio system] support node) and SGSN (serving GPRS support node). The GGSN is basically a packet router with additional mobility management features, and it connects with various network elements through standardized interfaces. The GGSN acts as a physical interface to the external packet data networks (e.g., the Internet). The SGSN handles packet delivery to and from mobile termi-
Gi
AUC
GMSC
H
Gc
HLR
Gr
C
Core Network
D
VLR MSC
Gf
Iu-CS
Other PLMN
Iu-PS Iu-PS
RNS
RNS
Iur
RNC
RNC Iub
Node B
AUC: Authenticatio n Center EIR: E quipment Identity Register
Gp
SGSN
Gs
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UTRAN
To IP Network
Gn
EIR
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GGSN
Iub
Node B
Node B
Node B
GGSN: Gateway GPRS Support Node HLR: Home Location Register MSC: Mobile Switching Center
PLMN: Public Land Mobile Network RNC: Radio Network Controller RNS: Radio Network Subsystem
SGSN: Service GP RS Support Node UTRAN: UMTS Terrestrial Radio Access Network VLR: Visited Location Register
. UMTS Network Architecture December 2002 • Volume 1, Number 1
1
nals. Each SGSN is responsible for delivering packets to the terminals within its service area. GGSN and SGSN are capable of supporting terminal data rates up to 2 Mbps. A UTRAN consists of one or more RNSs (radio network subsystems), which in turn consist of base stations (Node Bs) and RNCs (radio network controllers). The RNS performs all of the radio resource and air interface management functionalities. The UMTS network architecture inherits most of its structure from the GSM model in the UTRAN. This paper focuses on the differences between GSM radio system planning and UMTS radio system planning. UMTS uses WCDMA (wideband code division multiple access) as the radio transmission technology. It is claimed that TDMA (time division multiple access) RF planning is much more difficult than CDMA-based systems. This is true, in part, because of the interference issues. However, UMTS serves users with various demands, and many aspects of planning are more closely interrelated to each other in UMTS planning than they are in GSM planning. The major differences in the UMTS radio system planning process occur in coverage and capacity planning. In GSM, coverage is planned separately after the network is dimensioned (based on the market study), and capacity and frequency are planned in tandem. In UMTS, coverage and capacity are planned at the same time, because capacity requirements and traffic distribution influence coverage. Frequency and code can be planned separately. On the other hand, the wideband nature of WCDMA technology (5 MHz) compared with GSM (200 kHz) imposes new criteria in modeling the propagation environments.
Carrier 1
This paper outlines the challenges and solutions for planning and optimizing UMTS networks with respect to radio interface. WCDMA air interface specifications and their implications on transmission channel behavior and modeling are described first. Next, solutions are provided for system design, including coverage, capacity, code, and frequency planning. The analysis captures both design processes and engineering calculations. The critical optimization and monitoring of WCDMA network performance are then discussed. Finally, the paper concludes by summarizing the results and presenting the future roadmap.
UMTS RADIO INTERFACE
W
CDMA has been selected as the radio interface technology of UMTS networks for much of the world. It is totally different from the technology used in GSM or TDMA. The basic radio system planning philosophy used in GSM or TDMA does not change, but almost all of the detailed planning items concerned (e.g., the link budget) have to be checked and adjusted to be suitable for WCDMA technology. In addition, the radio system planning process has to be modified slightly from the traditional model because the traffic can vary from 8 kbps voice to 2 Mbps data and can be either circuit switched or packet switched.
It is important to understand the basic U MTS air interface features to plan radio interface of the network. The WCDMA specification has certain key features, which are listed in .
Carrier 2
0
B -10 d , r e w o P d -20 e z i l a m r o N
-30
-40 2150
2155
(MHz)
Spectrum of Two WCDMA Carriers with 5 MHz Channel Spacing (Unlike GSM and TDMA, the same carriers can be used in all of the cells. Thus, the reuse factor for this system is N = 1, while the GSM reuse factor is typically N = 4.) 2
Bechtel Telecommunications Technical Journal
WCDMA Air Interface Specifications
Modulation
DS-CDMA with QPSK
Chip Rate
3.84 Mchip/s
Duplexing
FDD and TDD modes
Channel Bandwidth
5 MHz with center frequency raster of 200 KHz
Service
Multi-rate and multi-service
Frame Length
10 ms frame with 15 time slots
WCDMA air interface is based on DS-CDMA (direct sequence CDMA) technology. The user data sequence is multiplied with a so-called spreading sequence, whose symbol or chip rate is much higher than the user data rate. This spreads the user data signal to a wider frequency band. The relation between user data rate and chip rate is called a spreading factor (SPF = Rchip/Rbit). The chip rate in WCDMA is 3.84 Mchip/s, and spreading factors are in the range of 4 to 512; therefore, the user net bit rates supported by one code channel are in the range of 1 to 936 kbps in the downlink. Up to three parallel codes can be used for one user, giving bit rates up to 2.3 Mbps. In the uplink, data rates are half of these figures, because of modulation dif ferences. The WCDMA standard includes two modes of operation: WCDMA/TDD (time division duplexing) and WCDMA/FDD (frequency division duplexing). In WCDMA/ FDD, the uplink and downlink signals are at different frequency bands. In WCDMA/TDD, the uplink and downlink signals are at the same frequency but are separated to different time periods. WCDMA/FDD will probably be the air interface deployed and used first. The nominal channel bandwidth of the WCDMA signal is 5 MHz. The specification provides the flexibility to define the exact channel center frequency of 200 KHz raster, so the actual channel separation might be smaller than the nominal 5 MHz, down to the specified minimum of 4.4 MHz. This has to be noted carefully because it might cause interference in the network. An example of the spectrum of WCDMA for two carrier frequencies is shown in . The WCDMA transmission is split into 10 ms radio frames, each of which consists of 15 pieces of 666 ms (2560 chips) time slots. The bit rate and, for example, channel coding can be changed in every 10-ms frame, offering very flexible control of the user data rate. Every time slot has bits reserved for pilot signal, power control (TPC bits), transport format indication (TFCI bits), and, if necessary, closed loop transmit diversity (FBI bits). The exact signal format and multiplexing are quite different in uplink and downlink signaling. Also, the dedicated and shared channels have several differences in signal format.
The radio propagation channel environment is divided into outdoor and indoor classes. The outdoor class is further divided into macrocellular and microcellular propa-
December 2002 • Volume 1, Number 1
gation environments. The macrocellular type of environment can contain dif ferent building densities (e.g., urban, suburban, or rural). Each of these propagation environments has special radio propagation channel characteristics. When considering the differences among GSM, TDMA, and UMTS radio interface performances, the key channel property is the delay spread, which describes the amount of multipath propagation in the propagation environment of the radio link. The delay spread can be calculated from the typical (estimated or measured) power delay profile, which describes the signal power as a function of the delay. The effect of multipath on the radio channel can also be described by the frequency domain properties of the radio channel. In the frequency domain, multipath causes frequency selective fading, i.e., signals at different frequencies have different fading (amplitude and phase). One frequency domain property of the channel is coherence bandwidth, Dfc. It can be calculated from the time domain property of delay spread. Coherence bandwidth is the minimum frequency separation of the two carriers that have significantly uncorrelated fading. shows the calculated coherence bandwidths typical for different radio propagation environments. The system is NB (narrowband) when the radio signal bandwidth is much smaller than the coherence bandwidth of the radio channel and WB (wideband) when it is much larger. Therefore, that system property is dependent on the typical propagation environment in which the system is used and could differ in different environments. Characteristics of GSM versus UMTS for Different Radio Propagation Environments ∆
Bandwidth
BW = 5 MHz
BW = 0.2 MHz
Urban
0.5
0.32
WB
NB/WB
Rural
0.1
1.6
WB
NB
Hilly
3
0.053
WB
WB
< 0.1
> 1.6
NB/WB
NB
< 0.01
> 16
NB
NB
Microcellular Indoor
The coherence bandwidth is related to the correlation of fading over the transmission bandwidth. In a propagation environment where a system is narrowband, fading is frequency nonselective or flat. In the wideband environment, fading for signal frequencies is uncorrelated and the fading is called frequency selective. Comparing the chip duration (0.26 ms) of WCDMA to the typical urban channel delay spread, it can be seen that the delay spread is larger than the chip duration. A WCDMA receiver achieves optimum performance by using all of the multipath components via a Rake receiver. The Rake receiver receives and combines different multipath delayed elements of the received signal. This combining method is an advantage of WCDMA compared with GSM and TDMA signals and increases the received signal power.
3
UMTS RADIO SY STEM PLANNING
T
he implementation strategy must be planned carefully because UMTS is a totally new system. UMTS operates in the frequency band of 2100 MHz, which is much higher than the 900 MHz and 1900 MHz typically used in GSM and TDMA systems. Also, the higher data rates for UMTS require better signal strength, Eb/No. These operating frequency differences, plus the higher data rates, mean that the radio propagation will not be equivalent. As a result, the old base station coverage areas are not necessarily valid in UMTS. Although reusing the old base station sites would be very cost-effective, they are not necessarily the most optimum locations for UMTS coverage. The decision to reuse the base station sites depends heavily on the implementation strategy and on the traffic forecasts.
The UMTS radio system planning process is similar to the GSM planning process. The phases of the planning process are: • • • • • •
Dimensioning Configuration planning Coverage and capacity planning Code and frequency planning Parameter planning Optimization and monitoring
The overall planning goal in any wireless system is to maximize coverage and capacity while meeting the KPIs (key performance indicators) and QoS (quality of service). shows the UMTS planning process. In particular, the figure shows the one key issue in UMTS coverage and capacity planning, namely that the traffic level has to be considered continuously in UMTS radio planning.
• Dimensioning - Traffic - Area - Coverage threshold •
The distribution of the traffic levels between voice and different data calls at each base station coverage area should be determined as accurately as possible. Also, the location of the different mobile users (or actually the link budget of each mobile user) should be known as exactly as possible. It is, of course, impossible to know the mobile user locations exactly; however, the more accurately they can be forecast, the better the radio network can be designed. Another key issue in WCDMA radio coverage and capacity planning is the regional traffic distribution, or the existence of traffic hot spots in the radio network coverage area. Base station locations should be selected so that they are always placed on the traffic hot spots, since this offers the best link budget for the mobile users served by those base stations. As the users move away from the base station, WCDMA throughput decreases. As shown in , placing base stations on traffic hot spots significantly reduces power levels in the radio network, which reduces i nterference and increases capacity. In the initial dimensioning phase, a fixed load is assumed for all base stations within the targeted area. The value for the load can be the maximum acceptable load for the cells or it can be the predicted load during the busy hour. If the highest acceptable load is used, the dimensioning is done according to the worst-case scenario, which may lead to an unnecessarily high number of sites. It is better to use the predicted load, because it will give more realistic results. In the detailed planning phase, the traffic distribution is used to allocate the predicted traffic to the planned cells. This may lead to situations in which the load between the cells can vary remarkably. Some cells may have a load very close to the maximum acceptable load, and some cells may have a fairly low load. Coverage targets must also be checked during this planning phase.
• Detailed Planning - Traffic - Site configuration - Coverage thresholds &
• Optimization and
•
•
Monitoring - Traffic - Coverage verification - Capacity availability
capacity requirements
UMTS System Planning Process
4
Bechtel Telecommunications Technical Journal
Although, in dimensioning, the traffic is assumed to be evenly distributed across a particular area, in reality, each area may have a different traffic density. Also, in dimensioning, propagation is assumed to be similar for all cells and all cells are assumed to be identical. During detailed planning, coverage predictions can be quite different among the cells due to propagation environment and traffic distribution. Typically, Monte-Carlo distribution of the mobile stations is used to predict instant traffic demand in the area of interest.
WCDMA coverage planning begins from the link budget calculation. The link budget in WCDMA, as in GSM, takes into account the base station equipment configuration and the base station antenna line configuration. The WCDMA link budget also contains some new parameters that are not used in the GSM link budget. A typical link budget for WCDMA is presented in . The link budget is calculated based on the following assumptions: • Uplink bit rate is 64 kbps and downlink bit rate is 144 kbps. • Predicted load in uplink is 30 percent and in downlink, 50 percent. • 1 W output power at the BTS is reserved for a connection. The link budget in is divided into five parts. In general information, the frequency band, chip rate, temperature and Boltzman's constant are given. In service information, the bit rates and loads for uplink and downlink are defined. Receiving end and transmitting end define the radio links in the uplink and downlink directions, respectively. Finally, isotropic path loss is defined
as the maximum expected path loss between the receiver and transmitter.
Coverage and capacity planning in WCDMA are interrelated. In low traffic areas, WCDMA planning is quite similar to GSM planning, because the load does not have a great impact on coverage. Of course, many details differ between the systems, but the main principles can be applied to both. In high traffic areas, unlike for GSM, there is no clear split between coverage, interference, and capacity planning of WCDMA.
The propagation predictions for WCDMA require the same planning phases as in GSM. First, the base station configuration and the link budget have to be defined. Also, the coverage threshold has to be well defined to exceed the required quality criteria but avoid unnecessary additional investments for the radio network elements. Moreover, the capacity targets and forecasts have to be well known at this phase because they have a strong effect on the base station coverage area. When the base station antenna height, coverage threshold, and capacity requirements are defined and the base station configuration is clarified in the link budget calculations, the actual propagation predictions process can start. Propagation measurements can be performed to finetune the propagation prediction model. When the prediction model is tuned, the final base station parameters can be used to make the propagation predictions. Optimized base station parameters can be evaluated when the planning criteria are defined. This planning threshold means that agreement must be reached on the reasonable QoS level required for the different geograph-
Hot Spot
Hot Spot
a) Lower coverage and capacity (inefficient design)
Hot Spot
Hot Spot
b) Higher coverage and capacity (optimum design) Correct UMTS Base Station Placement Impacts System Capacity December 2002 • Volume 1, Number 1
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Typical Link Budget for WCDMA Cell
Frequency
MHz
2100
Chip rate
Mcps
3.84
K
293
J/K
1.38E-23
Temperature Boltzman's constant
Load
%
30
50
Kbps
64.0
144.0
Thermal noise density
dBm/Hz
-173.93
-173.93
Receiver noise figure
dB
3.00
6.00
dBm/Hz
-170.93
-167.93
dBm
-105.09
-102.09
dB
1.55
3.01
Receiver interference power
dBm
-108.77
-102.09
Total noise (thermal + interference)
Bit rate
Receiver noise density Noise power Interference margin
dBm
-103.54
-99.08
Processing gain
dB
17.78
14.26
Required Eb/No
dB
5.00
4.00
Receiver sensitivity
dBm
-116.32
-109.34
RX antenna gain
dBi
18.00
0.00
Cable loss
dB
4.00
0.00
LNA gain
dB
0.00
0.00
Antenna diversity gain
dB
0.00
0.00
Soft handover diversity gain
dB
3.00
3.00
Power control headroom Required signal power Field strength Z = 77.2 + 20*log(freq[MHz])
TX power per connection TX power Cable loss TX antenna gain Peak EIRP Isotropic path loss
dB
0.00
0.00
dBm
-133.32
-112.34
dBµV/m
10.32
31.31
W
0.126
1.00
dBm
21.00
30.00
dB
0.00
4.00
dBi
0.00
18.00
dBm
21.00
44.00
dB
154.32
156.34
ical locations. The threshold also depends on whether the service has to be extended inside vehicles and buildings in different areas. The planning threshold is defined in GSM by starting from the mobile station sensitivity (for the forward link) and by adding the required clutter planning margins to the sensitivity value in each particular planning terrain bin.
WCDMA capacity planning is directly related to the link budget and, thus, to the base station coverage area. In the link budget in , only one type of service (64/144 kbps data transmission) was introduced, and the base station coverage was fixed for this service. It is 6
possible to have any type of service between the voice calls and 2 Mbps data traffi c in the WCDMA base station. This means that the base station coverage area is different for different users. (See .) Basically, the question is about the spreading factor, SPF, which varies significantly when comparing the 12.2 kbps voice call (SPF = 25 dB) and 2 Mbps data transmission (PG = 2.8 dB) connections. In the uplink direction, the main objective in capacity planning is to limit interference from the other cells to an acceptable level. Network planning can increase the uplink load by reducing other cell interference. This can be achieved by using buildings, hills, etc., as obstacles to block the interfering cells. Also, down-tilting is a very useBechtel Telecommunications Technical Journal
ful tool in limiting interference. In the downlink direction, two aspects should be considered: the interference from other cells and the power of the base station. The load equation for the downlink is similar to the equation for the uplink. However, in the downlink there is a new parameter called orthogonality. Orthogonality is a measure of how much the users in the same cell do not interfere with each other. In the downlink, users are much more orthogonal compared with uplink, because the base station is transmitting to all the mobiles with very accurate timing of the spreading codes.
• Which carrier(s) is used for macro cells? • Which carrier(s) is used for micro cells? • Is any carrier(s) reserved for indoor solutions? When making these decisions, the interference aspects should be considered. Carrier selection may affect intra-operator and inter-operator interference. For example, micro cells can cause high local interference for the operator's macro cells or another operator's macro or micro cells. Many potential problems can be solved by proper network planning, and one of the techniques for solving these problems is to properly select the frequencies.
In WCDMA, code and frequency planning are simple tasks from a network planning point of view. The system takes care of most of the code allocation. The main task for network planning is the allocation of scrambling codes for the downlink (Ref. 4). There are 512 sets of scrambling codes available, so the code reuse for downlink is 512. This means that code allocation is a relatively simple task, even though code capacity does differ for every user demand type. With more bandwidth user requests, a higher-level scrambling code is needed from the hierarchy of codes, and more code resources are drawn on. It is recommended that the allocation be done with the help of a planning system to avoid the possibility for an error in the manual allocation. The number of codes used in the early stages should be limited to allow for easier expansion of the network. Frequency planning has minor importance compared with GSM. At most, UMTS operators have two or three carriers, so there is not much to plan. However, the operators have to make a few decisions:
WCDMA OPTIMIZATION AND MONITORING
T
he WCDMA system, like the GSM system, needs continuous optimization and monitoring because the mobile users' locations and traffic behavior vary constantly. This monitoring requirement is emphasized in WCDMA, as in all CDMA systems, because the traffic demand can vary widely and this variation directly influences the radio network quality. The better and more accurately the traffic amount and locations can be modeled, the better and more efficiently (cost, quality, etc.) the radio network can be designed and implemented. The indicators that should be optimized and monitored are, for example: • • • • • • •
Traffic Traffic deviation Traffic mixture Soft handover percentage Average TX power Average RX power Drop calls
100 ) t n e c r e p ( a e r A / e g n a R l l e C e v i t a l e R
90 80 70 Relativ e Cell Range Relativ e Cell Area
60 50 40 30 20 10 0
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Bit Rate [Kbps] Relative Cell Range and Cell Area versus User Bit Rate Using WCDMA (Cell ranges calculated by using Okumura-Hata propagation formula [Ref. 3] and antenna height of 25 meters) December 2002 • Volume 1, Number 1
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Sector C
Sector A Sector C
Sector A Sector B
Sector B
a) Unbalanced load
b) Balanced load using smart antenna
Balancing Traffic Load and Boosting Capacity Using Smart Antenna • • • • •
Interference Handovers per cell Inter-system handovers Throughput Bit error rate and frame error rate
Many of the listed indicators should be collected on a cell and service basis, because the data may give hints on how to optimize the parameters to enhance the performance of the network. A detailed discussion of the WCDMA system is out of the scope of this paper. However, three particularly important optimization challenges for WCDMA cell sites are examined: traffic load balancing, handoff overhead management, and interference control. The fundamental problem of traffic loading is that cellular traffic is distributed unevenly among different geographical areas of the network. In fact, even within cells traffic tends to be distributed unevenly among the sectors. Such imbalance has the effect of locking up network capacity in underutilized sectors while causing blocking problems in the most heavily used sectors. Balancing the traffic load among the sectors of a cell alleviates the blocking and creates headroom for traffic growth. And by creating headroom at network hot spots, a targeted traffic load-balancing strategy allows more traffic growth and more efficient use of infrastructure and spectrum across the entire network. One way of achieving load balancing is to modify the antenna orientation and angular beamwidth of each sector to unify the traffic. This is possible using smart array antennas, as shown in . Another aspect of WCDMA optimization that directly affects cell site capacity is the management of handoff overhead. The soft/softer handoff feature of the CDMA air interface improves the quality and reliability of CDMA calls. However, because a given mobile may be in contact
8
with two or more cells or sectors at any given time, as in areas A and B in , soft/softer handoff implies a significant cost in capacity. After measuring the pilot strength in the area, the size of handoff zones within the cell footprint should be decreased. Handoff z ones should be shifted from high-traffic areas to low-traffic areas. Interference directly limits capacity of CDMA cell sites. One of the biggest interference problems in WCDMA networks is pilot pollution. Pilot pollution is often caused due to high-elevation sites with RF coverage footprints much larger than normal. The solution is to reduce the size of the coverage footprint. This can be accomplished by reducing the elevation of offending antennas, introducing downtilt, or reducing the transmitted power.
A
B
Example of Inefficient Design, Where a Large Area is Covered by Soft/Softer Handoff Bechtel Telecommunications Technical Journal
UMTS Radio Interface System Planning and Optimization
WCDMA radio propagation channel
• Channel delay spread is larger than chip duration; therefore, channel is wideband (frequency selective fading). • Rake receiver takes into account multipath.
WCDMA coverage and capacity planning process
• Coverage and capacity planning are related. • Code planning is unique to WCDMA systems, while channel planning is unique to GSM. • Traffic information and forecasting are necessary in coverage planning.
WCDMA link budget
• Planning covers the same basics as GSM, but uses different parameters. The WCDMA link budget depends on changes in bit rate and spreading factor.
Capacity planning
• Service depends on the distance from base station.
Frequency planning
• A simple process: The same frequency can be used for all the cells.
Code planning
• Allocation of scrambling codes is required for downlink.
Optimization and monitoring
• These factors are of greater importance than with GSM.
CONCLUSIONS
BIOGRAPH Y
T
As a senior RF engineer with Bechtel Telecommunications, Esmael Dinan has been instrumental in many aspects of the AWS Liberty RF engineering project and Bechtel GBU (Global Business Unit) research activities. His activities include design of the RF engineering data management system, development of the Liberty project RF engineering processes and procedures, Star21 Network auditing, and Dupont Cryogenic TMA performance verification and testing. Before joining Bechtel, Esmael was product manager for GMPLS control plane of the RAYStar DWDM optical switch at Movaz Networks, and lead network architect at Worldcom. Esmael has conducted research on access methods and performance modeling of 3G wireless communications and high-speed optical networks. He has authored more than 20 conference papers and journal articles and has filed a patent on a novel signaling mechanism developed for 3G cellular networks. Esmael received his Ph.D. in Electrical Engineering from George Mason University, Fairfax, VA.
he UMTS radio interface system planning has the same basic philosophy as GSM but varies in the detail mainly because of two reasons: the change of radio propagation channel that is a wideband type, and the change of modulation and transmission mechanism that is DS-CDMA. The major subjects and findings are again gathered in to summarize the major challenges concerning radio interface system planning in UMTS.
REFERENCES 1. T. Ojanpera and R. Prasad, "An Overview of Air Interface Multiple Access for IMT-2000/UMTS," IEEE Communications Magazine, September 1998, pp 82-95. 2. European Telecommunications Standards Institute, GPRS, GSM, EDGE, and UMTS Standard Documents, (http://www.etsi.org/getastandard/home.htm). 3. M. Hata, "Empirical Formula for Propagation Loss in Land Mobile Radio Services," IEEE Transactions on Vehicular Technology, Vol VT-29, No. 3, August 1980, pp 317-325. 4. E. Dinan and B. Jabbari, "Spreading Codes in Direct Sequence CDMA and Wideband CDMA," IEEE Communications Magazine, September 1998, pp 48-54. 5. T. Ojanpera and R. Prasad, WCDMA: Towards IP Mobility and Mobile Internet, Artech House Publishers, 2000.
December 2002 • Volume 1, Number 1
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Aleksey Kurochkin is currently director, Wireless Planning, in the Bechtel Telecommunications Technology group, a group that he originated. Aleksey has experience in international telecommunications business management and network implementation. Between engineering and marketing positions, he has both theoretical and hands-on experience with most wireless technologies. Aleksey came to Bechtel from Hughes Network Systems, where he built an efficient multi-product team focused on RF planning and system engineering. Aleksey is an electrical engineer, specializing in telecommunications and information systems, with an MSEE/CS degree from Moscow Technology University. Sam Kettani is a senior RF engineer at Bechtel Telecommunications. Currently, he is responsible for network design of mobile and fixed wireless networks. He has hands-on experience with wireless technologies and applications such as PCS and TDMA/CDMA and network performance analysis, microwave design, and engineering of fixed wireless networks using PTP (pointto-point) and PMP (point-to-multipoint) technologies. In previous positions, he was responsible for network planning and integration of various systems. Sam was also responsible for guidelines and processes, coordinating and managing numerous projects. Sam has a Bachelor of Science degree in Electrical Engineering in Telecommunications from George Mason University.
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