The document discusses Code Division Multiple Access (CDMA) technology. It begins with an agenda and introduction to CDMA, noting that it uses spread spectrum techniques to allow multiple users to share bandwidth. The history and development of spread spectrum and CDMA is then outlined from the 1950s to current 3G networks. Direct sequence CDMA transmission and reception methods are explained, involving spreading data with codes and despreading at the receiver. Issues like multiple access interference and multipath in cellular CDMA systems are also summarized.
High performance browser networking ch5,6Seung-Bum Lee
Presentation material including summary of "High Performance Browser Networking" by Ilya Grigorik. This book includes very good summary of computer network not only for internet browsing but also multimedia streaming.
The tutorial is designed for all those readers who are planning or pursuing the CDMA course to make their career in this field. However, it is also meant for the common readers who simply want to understand − what is CDMA Technology?
Successful interference cancellation with Blind Equalization method for MC-CD...IJTET Journal
Abstract— The increasing demand for wireless services has created the need for cost effective transmission techniques that can exploit scarce spectral resources efficiently. Inorder to achieve the high data rates needed to meet the quality of service requirements of future multimedia applications, MC-CDMA has been considered as good air-interface candidate, especially for the downlink. However, the user capacity of MC-CDMA system is essentially limited by interference. This interference can be mitigated by employing precoding techniques, IB-DFE based receivers and other efficient interference suppression techniques. In the proposed system, combined Iterative IA precoding at the transmitter with IB-DFE based processing at the receiver is suggested for MC-CDMA systems. The matrices for this nonlinear space-frequency equalizer are obtained by minimizing the overall MSE of all data streams at each subcarrier.
High performance browser networking ch5,6Seung-Bum Lee
Presentation material including summary of "High Performance Browser Networking" by Ilya Grigorik. This book includes very good summary of computer network not only for internet browsing but also multimedia streaming.
The tutorial is designed for all those readers who are planning or pursuing the CDMA course to make their career in this field. However, it is also meant for the common readers who simply want to understand − what is CDMA Technology?
Successful interference cancellation with Blind Equalization method for MC-CD...IJTET Journal
Abstract— The increasing demand for wireless services has created the need for cost effective transmission techniques that can exploit scarce spectral resources efficiently. Inorder to achieve the high data rates needed to meet the quality of service requirements of future multimedia applications, MC-CDMA has been considered as good air-interface candidate, especially for the downlink. However, the user capacity of MC-CDMA system is essentially limited by interference. This interference can be mitigated by employing precoding techniques, IB-DFE based receivers and other efficient interference suppression techniques. In the proposed system, combined Iterative IA precoding at the transmitter with IB-DFE based processing at the receiver is suggested for MC-CDMA systems. The matrices for this nonlinear space-frequency equalizer are obtained by minimizing the overall MSE of all data streams at each subcarrier.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
2. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
2
Agenda
• Introduction
• History of Spread-Spectrum and CDMA
• Introduction to DS-CDMA
• Cellular CDMA
• CDMA Capacity
• CDMA Cellular Applications
• Conclusions
• References
• Homework
3. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
3
Introduction
• CDMA is a modulation and multiple access scheme based on
the spread-spectrum communication technology
• Individual terminals use spread-spectrum techniques and
occupy the entire spectrum whenever they transmit
– Users share time and frequency allocations, and are
channelized by unique assigned codes
– Signals of different users are separated at the receiver by using
a correlator that captures signal energy only from the desired
user or channel
– Undesired signals contribute only to noise and interference
• In FDMA each user is given a small portion of the total
available spectrum
• In TDMA each user is allowed full use of the available
spectrum, but only during certain periods in time
F re q u e n c y
T im e
C o d e
H ig h d a ta ra te u s e r
U s e r C
U s e r A
U s e r B
4. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
4
History of Spread-Spectrum and CDMA
• Development of the CDMA technique dates back to the early 1950s when
different studies of the spread-spectrum technologies were started
• Basic by Claude Shannon and Robert Pierce in 1949
• In 1950 De-Rosa-Rogoff defined the direct-sequence spread-spectrum
method, the processing gain equation, and a noise multiplexing idea
• Price and Green filed the RAKE receiver patent in 1956
• In 1961 Manuski defined the near-far problem crucial for CDMA systems
• In 1970s several military and navigation applications were developed.
– Military with very low C/I, Anti-jamming applications
• Cellular applications proposed late 70s focused on narrowband systems
– In 1978 Cooper and Nettleton suggested a cellular spread-spectrum application
• During 80s Qualcomm investigated CDMA for cellular applications
– IS-95 standard 1993 and commercial networks introduced in 1995
• 3G wideband CDMA systems, such as CDMA IS-2000 and European
WCDMA developed from 1990s and still going on
– Commercial networks are opened at the moment
5. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
5
Spread-Spectrum Technology (1)
• Originally developed for military and navigation purposes
– secure means of communication in hostile environments
– Low Probability of Interception
• Cannot be easily detected by enemy communication equipment due to low
power spectral density, even lower than background noise
– Anti-Jamming
• Properties to combat intentional interference trying to sabotage
communication systems
• Nowadays feasible for commercial applications especially for mobile
communication systems
– It provides an efficient multiple access method for a number of
independent users sharing a common communication channel without
external synchronization methods
– DS-CDMA is probably the most interesting multiple access method
provided by spread-spectrum technology
6. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
6
Spread-Spectrum Technology (2)
• Transmission bandwidth is much larger than information bandwidth
• Bandwidth does not depend on the informational signal
• Processing gain = Transmitted bandwidth/ Information bandwidth
– Gp is also called the spreading factor and determines the maximum number of
simultaneous users or connections allowed in a communication system
– Determines the level of protection against multipath interference signals and
signal detection capabilities of a spread spectrum communication system
– In multipath situations the receiver observes spread-spectrum signals summed
with narrowband interference
– Determines the power ratio of the desired signal and interference after de-
spreading
– Low data rates such as speech have high processing gain compared to high
data rates
– High data rate means less processing gain and higher transmit power or
smaller coverage
i
t
p
B
B
G
7. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
7
Spread-Spectrum Technology (3)
• Classification of Spread Spectrum technologies
– Direct-Sequence
• Data is scrambled by user specific pseudo noise code at the transmitter side
– Frequency Hopping: The signal is spread by changing the frequency
over the transmitted time of the signal:
• Fast frequency hopping
• Slow frequency hopping
– Time Hopping
• The data is divided into frames, that itself are divided into time intervals
• The data is burst is hopped over the frames by utilising code sequences
• Also, a variety of hybrid techniques use different combinations
of these two basic techniques
8. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
8
Introduction to DS-CDMA (1)
DS-CDMA transmission and reception
B i
B i
B t
U s e r 1
U s e r 2
A f t e r s p r e a d i n g
N a r r o w b a n d s i g n a l
B t
C h a n n e l
B t
A f t e r d e s p r e a d i n g
B i
B i
P
P P
P
P
P
P
f
f f
f f f
f
9. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
9
Introduction to DS-CDMA (2)
Spreading
• A pseudo-random code is
generated, different for
each channel and each
connection
• The information data is
spread by a
pseudorandom code
• The resulting signal
modulates a carrier
• BPSK-signal has a 180-
degree phase shift when
the output of the
multiplication changes.
Data signal
Code signal
Data signal x Code signal
BPSK-modulated signal
1 chip period
1 bit period
10. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
10
Introduction to DS-CDMA (3)
De-spreading
• A pseudo-random code
is generated, matching
the anticipated signal
• The receiver acquires
the received code and
phase locks its own
code to it
• The received signal is
correlated with the
generated code,
extracting the
information data
rxb
pnr
dr
11. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
11
Introduction to DS-CDMA (4)
Pseudo-Noise (PN) sequences
• Produced by the pseudo-random noise generator that is simply a binary
linear feedback shift register, consisting of XOR gates and a shift register
– Ability to create an identical sequence for both the transmitter and the receiver
– properties of a noise-like randomness bit sequence
• PN sequences have characteristics such as
– Nearly equal number of zeros and ones
– Low correlation between shifted versions of the sequence
– Low cross-correlation with other user signals (interference) and noise
– Good autocorrelation properties with own signal in synchronisation
• M-sequences, Gold codes and Kasami sequences are examples of PN
sequences
Stage 1 Stage 2 Stage 3
Modulo 2 adder
Register output
12. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
12
Introduction to DS-CDMA (5)
Walsh Codes
• Walsh codes are the most common orthogonal codes used in CDMA
• Correspond to the rows of matrix known as the Hadamard matrix
• Walsh-Hadamard sequences can be used as spreading codes when users
are time synchronous
– The IS-95 system uses a 64 by 64 Walsh function matrix
• The motivation for the Walsh-Hadamard comes from noting that we can
contruct 2n orthogonal sequences of 2n from sequences of length of 2n-1
• Walsh-Hadamard codes will have poor autocorrelation and cross-
correlation at time offsets other than zero
– Synchronization of all users is required
– In a multipath channel, delayed copies may be received which are not
orthogonal any longer
– RAKE receiver is needed
Hn =
Hn-1 Hn-1
Hn-1 -Hn-1
Hn =
Hn-1 Hn-1
Hn-1 -Hn-1
13. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
13
Cellular CDMA (1)
Multiple Access Interference (MAI)
• The detector receives a signal composed of the sum of all users’
signals, which overlap in time and frequency
• MAI refers to the interference between users and is a factor, which
limits the capacity and performance of the system
• With CDMA systems, the same frequency channel can be used in the
adjacent cell, as long as multiple access interference is kept below a
given level
• MAI is directly proportional to the channel loading
• MAI can be divided in two parts: intra-cell and inter-cell interference
14. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
14
Cellular CDMA (2)
Multipath
• Reception of multiple, possibly interfering copies of the same signal
– Atmospheric reflection or refraction
– Reflections from ground, buildings, or other objects
• The tolerance of CDMA to interference extends also to a tolerance of
multipath
15. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
15
Cellular CDMA (3)
RAKE receiver
• Uses a multipath diversity principle
– Uses several baseband correlators to individually process several signal multipath components
– Correlator outputs are combined to achieve improved communications reliability and
performance
• Impulse response measurements of the multipath channel profile are executed through a
matched filter to make a successful de-spreading
– It reveals multipath channel peaks and gives timing and RAKE finger allocations to different
receiver blocks
– Tracks and monitors these peaks with a measurement rate depending on speeds of mobile
station and on propagation environment
• Number of available fingers depends on the channel profile and the chip rate
– The higher the chip rate, the more resolvable paths there are
– A very large number of fingers lead to combining losses and practical implementation problems
Correlator
Phase
rotator
Delay
equalizer
Code
generators
Channel
estimators
I
Q
I
Q
Combiner
Finger 1
Finger 3
Finger 2
Matched
filter
Input
RF signal
Timing and finger allocation
Output
Correlator
Phase
rotator
Delay
equalizer
Code
generators
Channel
estimators
I
Q
I
Q
Combiner
Finger 1
Finger 3
Finger 2
Matched
filter
Input
RF signal
Timing and finger allocation
Output
16. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
16
Cellular CDMA (4)
Near-Far Problem
• The problem arises when MS A and MS B are located in a same cell
with different distances from a BS
• If no power control were applied in uplink, the MS A would transmit
so high power that MS B would have no connection to the BS due to
too low SIR-values
• The MS A would be reserving a great amount of the capacity of the
cell
17. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
17
Cellular CDMA (5)
Power Control
• Power control is an extremely essential function when considering the
smooth operation and the capacity of CDMA-based systems
• The power control problem arises due to multiple access interference
• Each user looks like random noise to other users and causes
unnecessary interference to the system
• Power control is implemented to overcome the near-far problem and to
maximize the capacity of the system
– It tries to control the powers of the mobile stations in the system so that
the received powers at the base station stay equal
– It tries also to compensate the effects of slow fading and fast fading
– There is no near-far problem in downlink due to a one-to-many situation
• Power control forces all users to transmit the minimum amount of
power needed to achieve acceptable signal quality at the base station
18. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
18
Cellular CDMA (6)
Soft and Softer Handover
• Communications with a new base station on the same CDMA frequency
assignment before terminating communications with the old base station
• Softer handover occurs between two or more cells of one base station
• A soft and softer handover prevent the ping-pong behavior, and the dual base
station capability is a form of diversity that can increase capacity in a heavily
loaded system and also coverage in a lightly loaded system
• Soft handover helps to minimize with power control the interference both in
uplink and downlink directions
19. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
19
CDMA Capacity (1)
• Can be defined as throughput of bits or as the amount of simultaneous users in
the network receiving voice and data services with certain predefined quality
targets
• Interfering signals caused by users to each other rise, as the amount of users
gets higher in the network
• A balance between maintaining connection integrity and restricting
interference level is maintained by controlling the power of each user so that
signals arrive at their intended receiver with minimum required SIR-level
• Interference, coverage, and capacity are coupled tightly to together
• Capacity can be restricted by either transmission power constraints or by the
self-generated interference
– In the uplink, the system reaches its capacity when a mobile station does not have
enough power to overcome interference from the network, or a predefined loading
target of the network is met
– In the downlink, capacity is reached when no additional power is available to add
new users
– The power needed for either link is fundamentally related to Eb/No requirements
for different services
20. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
20
CDMA Capacity (2)
• Eb/No can be defined as in the following equation
• Where W is the chip rate, j is service activity factor, Rj is the baseband bit rate of a connection j, Pj
is received signal power from the connection j, and Itotal is the total received wideband power
including thermal noise power in the base station. Solving for P from previous equation leads to the
following equation
– where Lj
can be defined as the load factor of the jth mobile user’s connection in the uplink direction. For all
users in a CDMA network the uplink load factor can be defined as in the following equation
– where N is the number of uplink connections in the network
• The system has reached its pole capacity when the uplink load factor, UL, approaches 1. In reality,
there are two kinds of interference occurring. The effect of inter-cell loading can be taken into
account by the ratio of other cell to own cell interference, i. The uplink load factor then becomes to a
formula presented in the following equation
j
total
j
j
j
j
b
P
I
P
R
W
N
E
0
total
j
totql
j
j
j
o
b
j I
L
I
R
N
E
W
P
1
1
N
j
j
UL L
1
N
j
j
j
j
o
b
N
j
j
UL
R
N
E
W
i
L
i
1
1
1
1
)
1
(
)
1
(
21. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
21
CDMA Capacity (3)
• The curve has been calculated by inserting different values of load
factor in to 10log10(1- UL) giving the loss or the interference margin
in the link budget due to load. As the load factor comes near 1, the
interference margin is getting higher quite fast.
• Typically, load target should be maintained between 50 % and 75 %
because at those points the system is stable and can serve users.
Uplink Pole Capacity
0.000
10.000
20.000
30.000
40.000
50.000
60.000
70.000
0 0.2 0.4 0.6 0.8 1
Load factor
Loss
(dB)
22. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
22
CDMA Capacity (4)
• For the downlink the load factor is quite similar to the uplink
– where j is the orthogonality factor in the downlink.
• Orthogonal codes are employed in CDMA-based systems to separate the users
• The situation would be simple if there were no multipaths as orthogonality
would then remain when the mobile receives the signal from the base station
• If j = 1, then the base station signals are perfectly orthogonal, but in real
multipath radio channel the orthogonality factor is typically between 0.4 and
0.9; larger in microcells than in macrocells
• The ratio of other cell to own cell interference, ij, depends on the user location
and is therefore different for each user j
j
j
N
j
j
j
o
b
j
DL i
R
W
N
E
)
1
(
1
23. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
23
CDMA Cellular Applications (1)
IS-95
• Standard was finished in 1993 and first commercially launched in 1996
• Basic data rate is 9,6 kbps
• Chip rate of 1.2288 Mchips/s
• Allocated bandwidth is 1.25 MHz
• The IS-95B is packet data enhancement like GPRS is to GSM system
– “cdmaOne” was launched in 1999 with data rates up to 115,5 kbps
• Fixed spreading code of length 64; repeating bits provides lower data rates
• Uses pilot channel in downlink direction to provide synchronization, channel
tracking, and handover functions
• In the uplink direction, orthogonal modulation is used, which permits the more
robust noncoherent demodulation to be used
• In IS-95, all base stations use the same scrambling code (short code) to
distinguish among their transmissions, but with different timing offsets
– GPSS receiver in every base station provides base station synchronization.
24. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
24
CDMA Cellular Applications (2)
CDMA2000
• The third generation evolution phase of IS-95A/B
• It can offer up to 307 kbps data rates (compare to EDGE)
• CDMA2000 can use same 1.25 MHz as IS-95/cdmaOne
1xEV-DO/DV
• 1xEVDO (Data Only) and 1xEVDV (Data&Voice)
• Can offer high-speed data rates from 2,4 Mbps to 3,09 Mbps
WCDMA
• The faster chip rate of 3,84 Mchips/s implies that WCDMA receiver can provide greater
multipath resolution and with a RAKE receiver, this implies greater frequency diversity
due to wider bandwidth, 5 MHz
• Data rates up to 384 kbps for circuit switched and up to 2 Mbps for packet switched data
• Downlink spreading factor = 4 - 512 and uplink spreading factor = 4 - 256.
• Coherent detection on both uplink and downlink direction by using pilot bits in
transmission
• HSDPA 3GPP R5 using new modulation (QPSK+16QAM) and coding schemes to give
higher data rates for packet switched data in WCDMA
25. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
25
Conclusions
• DS-CDMA is probably the most interesting multiple access method
provided by spread-spectrum technology
• Data is scrambled by user specific pseudo noise code at the transmitter
• Through RAKE receiver multipaths can be used in advantage to
improve receiver performance by capturing the energy in paths having
different transmission delays
• Power control and soft handover must work or there is no cellular
CDMA as we know
• Interference, coverage, and capacity are coupled tightly to together in
CDMA systems
• Nowadays systems such as CDMA2000, its evolution versions, and
European WCDMA are becoming more and more popular as the
networks are opening commercially around the world
26. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
26
References
• [1] Simon Haykin, Michael Moher: Modern Wireless
Communications, Prentice Hall 2005, pp. 258-338.
• [2] Samuel C. Yang, CDMA RF System Engineering, Norwood MA,
USA, Artech House Inc., 1998, 280 pp.
• [3] Tero Ojanperä, Ramjee Prasad, Wideband CDMA for Third
Generation Mobile Communications, Norwood MA, USA,
Artect House Inc., 1998, 439 pp.
• [4] Jerry D. Gibson, Elaine M. Gibson, The Mobile Communications
Handbook, 2nd Edition, Boca Raton, Florida, USA, CRC Press
LLC, 1999, 600 pp.
• [5] John G. Proakis, Digital communications, 3rd Edition., New
York, USA, McGraw-Hill, 1995, 928 pp.
• [6] Harri Holma, Antti Toskala, WCDMA for UMTS, Radio Access
For Third Generation Mobile Communications, Chichester,
England, John Wiley & Sons, Ltd., 2000, 322 pp.
27. 11/30/2004 Tommi Heikkilä
S-72.333 Postgraduate Course in Radio Communications
27
Homework
1. a) Construct Walsh-Hadamard sequences of length of 8 if
1. b) Spread following data signal, S, with 3rd row sequence of the
Walsh-Hadamard matrix constructed in phase a)
S = [1 –1 –1 1]
2. Why are power control and soft handover so important features in
CDMA cellular systems?
H1 =
1 1
1 -1