CDMA Technology

CDMA engine roomCDMAWhat CDMA Technology is all astir(predicate)?The first proposals for CDMA cellular vanes in the the States and Europe (1978-1980) yielded to alternative projects, which later evolved into the GSM and DAMPS archetypes. However, in the mid 1990s the 2G standard IS-95 was put transport, resting on a fully spread spectrum/ CDMA platform. At a cosmic pace, net deeds of this standard (later named cdma unity) gained wide recognition in America, Asia and the former Soviet Union countries. The great success of IS-95, as well as wary analysis and further experiments, had led to acceptance of the spread spectrum/CDMA philosophy as the basic platform for the major(ip) 3G peregrine piano tuner particular propositionations UMTS and cdma2000. Both of them atomic go 18 now in the pre-operational stage and undoubtedly give become the chief(prenominal) mobile discourse instruments for the next decades.As we know it is all close to quaternate access, so nine-fold acc ess is subdivided into* Contention- Based Techniques* Conflict-free technique.CONTENTION petty(a) CONTROLThis is non in the scope of this projectCONFLICT let off CONTROLIt involves the division of corpse resources into fixed channels which be than uncommunicative by transmit/receive pairs of communication. This is beneficial for channels which conduct lawful and continuos access to a channel like video and audio.Code portion Multiple AccessIn CDMA systems, channels are defined by the engrave not by time or absolute frequency. Spread Spectrum believe on pseudo-random waveforms termed spreading ordinances to create noise-like transmisision.if exploiters stack be given varied codes that have low cross-relation properties, channels whoremaster be defined by these codes.In CDMA channels are defined by Spreading Codes, eg with the figure sequence CDMA two marks can be defined asWhere a1(t) and a2(t) are spreading codes that define the channel of each exampler symbo l and accordinglyce cross relation surrounded by a1(t) and a2(t) dictates the death penalty of CDMA.1Technology behind CDMACDMA engineering science is based on the Spread Spectrum communication technique, in the past few years this technology has created a revolution in the wireless communication technology today the drug users are victimisation 3-G wireless selective information function and applications like e-mail, and videos calls etc. that requires fast transmission without every loss of entropy and quality. 2Importance of TechnologyCDMA support all channel sizes (5 MHz, 10 MHz, etc.) declare oneself circuit and packet info rates up to 2 Mbps, combine advanced multimedia capabilities, and include a framework for advanced 3G utter wait ons, including voice over packet and circuit entropy. The interaction amidst mobiles in the self alike(prenominal) channel is the distinguishing characteristic of CDMA,CDMA Features and Serviceshttp//e-articles.info/e/a/ deed/CDMA --Features-and- run/The features and faster access of data provided by CDMA technology leads the life of an single(a) to the ease of that comfort level that they need not to worry about anything in respect to the communication level.Benefits of CDMA Affecting human Life1 Primary voice features -.a) skirt advancement Busy (CFB)/Call Forwarding Busy No Answer (CFNA)/Call Forwarding Busy compulsory (CFU) CFB, CFNA, and CFU allow a called subscriber to have the system send ingress calls, chip inressed to the called subscribers directory number, to another directory number (forward-to number), or to the called subscribers designated voice mailbox.b) Conference call (CC) CC provides a subscriber with the ability to conduct a multiconnection call, i.e., a simultaneous communication in the midst of three or more parties (confereesc) Do Not Disturb (DND) DND prevents a called subscriber from receiving calls. When this feature is active, no future calls shall be offered to the subscr iber.2 Short essence Service Featuresa) Short Message Deli precise-Point-to-Point Bearer Service (SMD-PP). SMDPP provides bearer service mechanisms for delivering a in short pith as a packet of data between two service users, known as short message entities (SMEs). The length of the bearer data may be up to 200 octets.b) Cellular Paging Teleservice (CPT) CPT conveys short textual messages (up to 63 characters) to an SME for display or storage.3 info tiltThe best data transfer technology it has to offer is the EVDO technology, allowing for a supreme down consign speed of about 2mb/s (about 700kbps in practice), which is similar to what a DSL line has to offer. EVDO is not available everywhere yet and requires a cell think that is EVDO ready.4 Global Positioning Systems (GPS)The main receipts of using CDMA cell phone signals for reference clock purposes is that they work go against inside buildings, thus often eliminating the need to mount a GPS aerial outside a building. ht tp//www.allinterview.com/viewpost/165996.htmlModulation TechniqueThe modulation technique apply in CDMA (specifically in wireless communication in mobile network) is dual-channel QPSK (hybrid kind shift keying (HPSK) or saucy daedal quadrature phase shift keying (OCQPSK))The methods utilise by dual-channel QPSK to Modulate are- fresh spreading Code Scrambling code with Walsh Rotator Pseudorandom codes (Scrambling)Orthogonal spreading CodeSpreading transforms each data symbol into multiple data chips. This ratio (number of data chips/symbol) is called the spreading factor (SF). Thus, it increases the signal bandwidth. Data symbols on the I(real, or In-phase data component) and Q(imaginary, or Quadrature-phase data component) branches are have with the channelization codeIn downlink it is employ to separate different users inside one cell, scarce in the uplink only to separate the different services of one user Generation of channelization codeAllocation of codeIt is lay dow ning the root of code tree. It employs the spreading factors 4 by means of 512, in which 4 to 256 appears in uplink, and SF 512 is added to the SF catalogue in the downlink direction. It in like manner shows how the codes can be allocated. specimen If the code C8,2 is allocated, then from its subtree no codes can be apply (i.e. C16,4, C16,5, C32,8). These subtree codes would not be orthogonal with their parent code. Scrambling code with Walsh RotatorHow it works?ExampleOriginal data chip divided into its I and Q components (1,1) and a complex scrambling signal (-1,1). When complex scrambling takes place, the phases of these signals are added together(45 + 135 = 180) and the eventing signal constellation is (-1,0).The distance of I and Q from origin represents the agent level of the signal. If the maestro data signal uses equal creator levels for control and data channels, then the constellation points will be (1,1), (-1,1), (1,-1). When they are scrambled using a complex scra mbling code, the result always lies on either the I or Q axis that is, mapped into the constellation points (1,0), (0,1), (-1,0), and (0,-1).This means that these phase shifts cannot cause zero crossingsPseudorandom codes (Scrambling)The orthogonal codes can only be apply when the signals applying them are time synchronous. So for asynchronous users in the uplink direction if orthogonal spreading codes alone were used in the uplink, then they could easily cancel each other.So to get well this situation pseudorandom codes are used. In this procedure, the signal, which is spreaded (full bandwidth) with an orthogonal spreading code, is further unite (means XOR) with a pseudorandom scrambling code. This scrambling code is either a long code (a notes code with a 10-ms period) or a short code S(2) code raw material RequirementsHardwareSoftwarePLANET EVIt is used to designing military rank of network problems also provides a comprehensive set of coverage and hoo-hah analyses of diffe rent cell sites.Bangarpet%20Coverage%20MEIRPTems Investigator* It provides view of the network.* It can evaluate the functionality of Call dishing and received base station signal qualityTems DeskcatIt estimates the performance of the network infrastructure. It can provide a comparison of oue network with the competitors networkAntenna EditorIt provides a view of Horizontal and vertical sort of antenna.SkillsFault precautionThe fault report must contain bountiful information so that the circumspection system can make the ripe(p) analysis and react correctly.Configuration managementOnce the number of subscribers increases, unseasoned capacity is needed thus, new equipment must be boughtPerformance management Traffic levels within the network, both user data and control signalling check mark of the network configuration Resource-access measurements QoS Resource availabilityRoaming managementA roaming symmetry is a contract between the home-network operator and the serving-net work operator drillr equipment managementThis is a feature that allows a network operator to trace the exceptional subscriber within the network.Software managementThe main bundle-management process can contain the following stages Delivery of software from the vendor Forwarding of the software to network elements or element managers Validation of the software to ensure that it is not corrupted Activation of the software to an executable stateENHANCED contributor AUTHENTICATION ALGORITHMThis method utilizes the Authentication and Key Agreement which provides plebeian authentication between a base station and mobile goal with change magnitude key size. Mutual authentication overcomes the problem of false base station attacks, thereby preventing the voice privacy or private individuality information of the subscribers from being compromised. The ESA algorithm also dismantles the cryptographic attacks such as reconstruction attack and list attack, thereby enhancing the security of existing CDMA systems. The cloak results also clearlyIndicates that ESA based systems consume less big businessman and the fracture rate is also less when compared with CAVE based system. Thus, the Enhanced reviewer Authentication algorithm enhances the security of the CDMA systems.Advantages of CDMA1. No frequency management In CDMA we are not required to use different frequency where as in both TDMA and FDMA the frequency management is always a critical task. Since there is only one channel in CDMA, no frequency management is needed.2. No Guard Time in CDMA. In TDMA uses the invention of guard time so as to avoid interference between simultaneous users whereas in typeface of CDMA we are not required to add guard time which result in cost-efficient use of bandwidth.3. No Hard Handoff As we CDMA is based on code sequence and uses the same frequency, the connection to the new cell site can be make without breaking the connection of the current cell. And it also requires less provide, which reduces interference and increases capacity.4. Use of Rake Receiver In CDMA have profligate receiver which is multiple receiver in one which identifies three multi-path signals and combines them to make a very strong signal. Both mobile and cell site use rake receivers.Whereas in case of GSM handsets it picks the first the first signal it gets. No intimacy what is the strength of signal?5. Power Ad in force(p)ment in CDMA- in CDMA handset itself can adjust at which they transmit the signal. This insures that base station is receiving signal at the power which is needed. Both forward and reverse link uses power control techniques.Where as in case of GSM network handset will transmit at the fix setting whatever the distance between handset and base station is. The base station would face highly strong signal from the nearer and extremely low from the farer device which result in Near-Far Problem.6. CDMA can have this flexibility with their own service that stor es data on the operators database. So if the cell is lost then its contact any other information can be recovered where as in case of GSM if mobile is lost then SIM is also lost.7. CDMA capacity is almost 10-20 times to FDM and approx 4 times to TDMA.8. More coverage comparatively GSM One of the main advantages of CDMA is that dropped only when the phone is at least twice as far from the base station.9. CDMA also have better security and high data and voice transmission quality because of the spread spectrum technology it uses, which has increased resistance to multipath distortion.Disadvantages of CDMA 1. Connection fixed with the Handset- The main problem with CDMA technology that client faces it that it does not allow to change handset easily because many functionality is enter in the handset whereas in case if it uses SIM card that identifies a user and stores the information in the handset. The SIM card can be swapped between handsets, which modify to move all the contacts to the new handset with ease.2. international roaming In case of international roaming handsets with GSM is far better than CDMA handsets because GSM is used in most the markets crossways the globe.3. Battery Life- The battery life in case of CDMA is lesser as compared to TDMA because CDMA handsets transmit data all the time but TDMA does not require constant transmission.CDMA is best suited for death penalty1. For Microcell and in-building Systems CDMA is probably the best system for microcell and in-building systems. The embedded microcell shares the same frequency and has full connectivity with the overlaying macrocell. The capacity of microcell and macrocell is derived and simulated at various traffic distributions. The microcell capacity is 1.03 to 1.12 times the capacity of a reparation cell. The capacity of the combined microcell and macrocell is 2.00 to 2.11 times that of a regular cell. The microcell and macrocell performance is also analyzed in terms of RF reliability , soft hand-off factors, and interference and power levels. The macrocell RF reliability will degrade more seriously than that of the microcell. The radio receiver hand-off factors of the microcell are about 11% higher than that of the macrocell. The average required forward traffic channel power of the microcell is about 10% less than that of the macrocell. Microcell engineering guidelines in a commercial-grade CDMA system are also provided. The results show that embedding the microcell in an existing CDMA network could be a very efficient way to improve hot-spot capacity and dead-spot coverage.12. For boorish area CDMA is that dropped only when the phone is at least twice as far from the base station. So it will be profitable in constructing the number of tower where in case of GSM it will be more because its coverage area is less. CDMA handsets can also work with anolog signal we can get at rural areas where digital signals cannot be transmitted.3. For Dense area CDMA uses sp read-spectrum technology and a modified(prenominal) coding scheme to allow multiple users to be multiplexed over the same physical channel, coding provides more users for the same amount of available power used in other system.Problems In Implementation of CDMA Spectrum Shortage The major problem faced by CDMA technology is lack of available spectrum and this is hinder their subscriber growth. In India CDMA operators are having problem in allocation of spectrum in 1900 MHz band which is common in other regions. According to B.B. Anand (President for restrictive Affairs at Reliance Infocomm ) It is of the utmost importance that the 1900 MHz spectrum be allocated to CDMA operators in India to ensure that the region remains part of the international federation of roaming wireless subscribers worldwide,1In India the band was allocated to self-denial Services for their mobile communication usage. However upon the launch of mobile communication services for public, coordination was sought from the Defense department to make the spectrum available for mobile services. The Defense is releasing some spectrum through auction but it is opposed by the GSM operators on the commercial ground for preventing growth of CDMA Low performance in hilly regions- The towers in CDMA interfere with each other and normally they are installed on often shorter towers and because of this CDMA (IS-95 standard) may not perform well in hilly terrains and India has kitty of such region in north region. Near Far effect- In Near Far effect the code transmitted from a transmitter (A) to receiver is interfered by another transmitter (B) which is nearer to the receiver as compared to sender transmitter and this make difficult for identification of the original signals by the receiver .This effect became a major obstacle for successful implementation of CDMA technology.It is very expensive to solve the near far problem in a CDMA system. The precision power control algorithm are used to s olve near far problem which consists of open loop power control and closed loop power control and this make a CDMA transreciever very complicated in both hardware and software implementation. existing of Base Stations, where coverage area shrinks under load. In CDMA as number of subscribers using a particular sit increases the range of that site goes down. In other words unlike GSM where number of users are finite but in CDMA users are not finite and in more load the voice quality goes down.Design And Implementation of CDMACDMA basicsThe CDMA technology works on basic principle of communicating through specific code on available frequency instead of assigning a specific frequency. Since users are specified by code they are able to use same carrier frequency and this eliminates the frequency reuse problem encountered in other technologies.ImplementationAt Sender sitecdmaSteps in generation of CDMA signals1. Analog to Digital Conversion of Voice CDMA uses Pulse code Modulation (PCM) for converting parallel voice or audio to digital signal. This process is also known as digitalization.2. Voice Compression CDMA uses a special device VOCODER to do voice compression. They are located at the BSC and in the phone. While talking we give space or pause between words and CDMA takes advantage of these pauses in speech activity by using a variable rate vocoder. There are four data rates at which vocoder compresses the voice signal and they are , , 1/8 and Full. Vocoder uses its full rate when a person is talking very fast. It uses the 1/8 rate when the person is nearly silent.3. Encoding and Interleaving Encoders and interleavers are construct into the BTS and the phones. They build redundancy into the signal so that information lost in the transmission can be recovered. CDMA uses convolutional encoding to encode audio signals provided by VOCODERS.Interleaving is used to reduce the effects of burst errors and recovering lost bits.4. canalisation The encoded data after encoding and interleaving is again encoded to separate it from other encoded data. afterward that encoded signals are spreaded over the entire channel.CDMA uses WLASH code to channelize user on the forward or upward link i.e. from BTS to mobile and Pseudorandom noises to channelize user on reverse link or downward link i.e. from mobile to BTS.5. Converting digital signal to a Radio Frequency (RF) signal. The channelized data from all calls are combined into one signal and then it is converted into radio frequency signal for transmission.A more relevant and self instructive example is show below of transmission through base station. As explained above each conversation is compressed with a vocoder and the takings is treble by a convolutional encoder that adds redundancy for error checking. The encoded bit are then channelized and all calls are combined and modulated onto a carrier frequency.At Receiver siteAt receiving site the steps followed are just opposite of sender site1. Co nversion of RF signal to digital signal2. Despreading the signal3. Deinterleaving and decoding4. Voice decompression5. Digital to analog voice recoveryRF signal are converted into digital signal by quantization into bits (chips) by the analog-to-digital converter (ADC). The output is deschannellized and decoded through a decoder know as Viterbi decoder which corrects the errors using the convolutional code. The output goes to the vocoder for decompression and then to digital-to-analog converter (DAC), which decompresses the bits and turns them back into waveforms (sound).Reference1. Unknown (14 Oct 2004).CDMA receiving set Community Calls For Harmonized Spectrum Allocation.useable http//www.3g.co.uk/PR/October2004/8463.htm Last accessed 3 March 2010.2. Available http//www.pangolinsms.com/images/cellular-standards/cdma-large.gif Last accessed 30 March 2010.3. Available http//www.yourdictionary.com/computer/cdma Last accessed 16 March 2010.4. Available http//www.cdmauniversity.com/Pr odTech/cdma/training/cdma25/intro/modules.html Last accessed 23 March2010.