There are following categories of handover (also referred to as handoff):

During the cell search, the UE searches for a cell and determines the downlink scrambling code and frame synchronisation of that cell. The cell search is typically carried out in three steps:

Step 1: Slot synchronisation

During the first step of the cell search procedure the UE uses the SCH's primary synchronisation code to acquire slot synchronisation to a cell. This is typically done with a single matched filter (or any similar device) matched to the primary synchronisation code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output.

Step 2: Frame synchronisation and code-group identification

During the second step of the cell search procedure, the UE uses the SCH's secondary synchronisation code to find frame synchronisation and identify the code group of the cell found in the first step. This is done by correlating the received signal with all possible secondary synchronisation code sequences, and identifying the maximum correlation value. Since the cyclic shifts of the sequences are unique the code group as well as the frame synchronisation is determined.

Step 3: Scrambling-code identification

During the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified through symbol-by-symbol correlation over the CPICH with all codes within the code group identified in the second step. After the primary scrambling code has been identified, the Primary CCPCH can be detected and the system- and cell specific BCH information can be read.
If the UE has received information about which scrambling codes to search for, steps 2 and 3 above can be simplified

High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design.

In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbps to support packet-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even higher data transmission rates up to 20 Mbps. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.

Currently (2002) 3GPP is undertaking a feasibility study on high-speed downlink packet access.

TDD WCDMA uses spreading factors 4 - 512 to spread the base band data over ~5MHz band. Spreading factor in dBs indicates the process gain. Spreading factor 128 = 21 dB process gain). Interference margin is calculated from that:

Interference Margin = Process Gain - (Required SNR + System Losses)

Required Signal to Noise Ration is typically about 5 dB System losses are defined as losses in receiver path. System losses are typically 4 - 6 dBs Overview of Spreading Process

After the first and second chapter of my self learning, here we go the third chapter titled Antennas for WiMAX. Just like traditional Wireless System, there are 3 kinds of antenna used for transceiving Radio Access Signal i.e., Omnidirectional, Sectoral, and Point to Point. The use of those antenna depends on it’s application.

1. Omnidirectional, broadcast 360 degree suitable for large area rural environment.

2. Sectoral, broadcast on intended area: 60, 90, and 120 degree. This kind of antenna is suitable for urban environment which has lage population on a certain area.

3. Point to Point Antenna is used for point to point communication, i.e., Microwave link, backbone etc.

(pictures are filched from wimax.com). If you need to read WiMAX Application material, please visit this my previous post, here

After we have discussed about those traditional antennas, now we are going to discuss advanced antenna technology in WiMAX.

1. Antenna Diversity,

Using two or more receiving antennas on a wireless device to eliminate multipath signal distortion. Typically, the signal from the antenna with the least noise (best SNR) is chosen, and the other antenna is ignored.

There are three techniques in diversity scheme:

1. Space Time Coding (Alamouti Code), is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. STCs rely on transmitting multiple, redundantcopies of a data stream to the receiver in the hope that at least some of them may survive the physical pathbetween transmission and reception in a good enough state to allow reliable decoding. (resource: http://en.wikipedia.org/wiki/Space–time_code) Space time codes may be split into two main types:

Space–time trellis codes (STTCs)^[1] distribute a trellis codediversity gain. over multiple antennas and multiple time-slots and provide both coding gain and

Space–time block codes (STBCs)^[2][3] act on a block of data at once (similarly to block codes) and provide only diversity gain, but are much less complex in implementation terms than STTCs.

Matrix A MIMO

Matrix A MIMO implements the rate 1 Space-Time Coding scheme (commonly known as the Alamouti Code). This technique captures diversity gains by sending a single data stream in two parts out of two antennas, interleaved with transformed/conjugated versions of the same information, so that the receiver has

higher probability of successfully extracting the desired signal. Matrix A achieves a spatial diversity order of two, but does not set out to achieve combining, interference mitigation, or spatial multiplexing gains.

Matrix A MIMO delivers higher link robustness, reducing fade margin by 5 to 6 dB, with little or no degradation as subscriber mobility increases. The impact on end-user data rate is small; reduced fade margin may allow the use of marginally higher order of modulation, but it is not comparable to the 2x throughput gain achieved by comparable Matrix B MIMO through spatial multiplexing. Matrix A MIMO is useful in networks with light loading and relatively high subscriber mobility.

We will now look at how Matrix A MIMO works in a little more detail.

Consider a Matrix A MIMO system, consisting of 2 Transmit and 2 Receive antennas as depicted below.

The signal received by one of the antennas at the receiver is a mixture of the signals transmitted from both of the transmit antennas. The receive signals can be expressed by the following simplified equations:

Rx1(f) = (H1,1(f) x Tx1) + (H2,1(f) x Tx2)

Rx2(f) = (H1,2(f) x Tx1) + (H2,2(f) x Tx2)

The receiver sees a combination of the transmissions from the two transmit antennas and needs to recover the actual transmitted signals. MIMO systems achieve this by using coding schemes that define which signal should be transmitted and when in order to make it possible to recover the original signal. These coding schemes are called ‘Space-Time’ codes because they define a code across both space (antenna

separation) and time (symbols).

Matrix A MIMO is a Space-Time Block Code, so called because the code operates over a block of data. Block codes require less processing power to decode than convolutional codes.

The following matrix defines how the code works:

X is the output of the encoder and S1 and S2 are the input symbols into the encoder. ‘*’ denotes a complex conjugate of the symbol. The rows of the matrix represent the transmit antennas and the columns represent time. Each element of the matrix indicates which symbol is to be transmitted from which antenna and when.

X is the output of the encoder and S1, S2 are the input symbols into the encoder. The row of the matrix represent the transmit antennas; there is no time element because Matrix B MIMO operates over a single time interval. Each element of the matrix indicates which symbol is to be transmitted from which antenna. In this

system 2 symbols are transmitted in a 1-symbol time duration thus providing a twofold capacity increase.

For complete reading, you may read this Smart Antenna System whitepaper.

This is my first Chapter on my own WiMAX RF Engineer self learn. As I mentioned before in my post this first chapter contains Module 1material:

6 WiMAX Applications (after walking around the web, I found an interesting material from Intel)

On the picture above there are 6 applications and it’s architecture which is grouped in to three items:

1. Access (Appropriate standards: 802.16d-2004 and 802.16e)

• Fixed Outdoor
• Backhaul

2. Portability (Appropriate standard: 802.16e)

• Nomadic Metrozone
• Fixed Indoor
• Enterprise, Campus Piconet

3. Mobility

• Mobile Application

Standards Specification

Spectrum availability, there are two kind of spectrum frequency:

• Licensed Spectrum
• Unlicensed Spectrum

• • From picture above we can conclude, WiMax Main RF Bands are: 2.3 GHz, 2.4 GHz, 2.5 GHz, 3.5GHz, 5.8 GHz, and (maybe) 700 GHz.

802.16e Standard Enhancement.

First WiMax standard was published in April 2001 and completed in October 2001. And as amendment 802.16a was approved in 2003. After 2003 the standard development continuous and breed 802.16d in 2004. And then in 2005, 802.16e was approved and add the mobility to the standard.

So what is the different between 802.16d and 802.16e? Well… let me show you what I’ve got

• 802.16d
  1. NLOS application and indoor CPE are supported.
  2. Beam forming Antenna
  3. OFDM Subchannelization
  4. FBWA Technology (wireless DSL Alternative)
• 802.16e (called “Mobile WiMax)
  1. Supports Portable BWA
  2. Operated on 2.3 GHz, 2.5 GHz and 6 GHz
  3. Handoff and Roaming Support
  4. Scalable OFDMA, OFDMA with subchannelizatoin

From the brief introduction above, we can conclude that 802.16e enhancement is about mobility, as we can see it supports Portable BWA, Handoff and Roaming.

As I am studying WiMAX RF Technology now, the tittle above is my certification wish list ( I hope I can take it… ). While I’m dreaming about this kind of certification, I do some web walking and find this Certification syllabus:

WiMAX Forum RF Network Engineer Certification™

Module 1: WiMAX Network Design Options

• List six applications of WiMAX technology
• Match each application to its WiMAX specification, frequency band, and architecture
• Describe five 802.16e mobile WiMAX enhancements

Module 2: Review of RF Fundamentals

• Calculate power levels in dBm, Watts and ìV/m
• Apply Nyquist and Shannon observations to calculations of the bandwidth of channels, and to WiMAX’s adaptive modulation and coding

Module 3: Antennas for WiMAX

• List three antenna diversity techniques
• Describe the operations of two types of MIMO systems and two types of Advanced Antenna Systems

Module 4: RF Design Considerations for WiMAX

• Describe the sources of noise based on bandwidth and operating frequency
• Determine the system noise floor based on bandwidth and Noise Figure
• Determine system performance based on C/N and Eb/No

Module 5: Performing a WiMAX Link Budget

• Determine LOS and NLOS Maximum Allowable Path Loss (MAPL) based on system parameters
• Determine power settings for a balanced path
• Use spreadsheets to design for specified lognormal fading probability
• Perform a link budget based on manufacturer’s equipment parameters and system requirements

Module 6: WiMAX Path Loss Modeling

• Determine expected point-to-point link performance using an analytical path loss model
• Calculate expected NLOS performance using an empirical path loss model
• Determine the amount of margin required, based on lognormal fading

Module 7: Frequency Reuse in Fixed and Mobile WiMAX Networks

• Design the frequency reuse plan for your WiMAX network, working with your equipment vendor
• Diagram FUSC and PUSC permutation zones
• Discuss several reuse proposals for mobile WiMAX networks

Module 8: WiMAX Performance and Coverage Considerations

• Explain and follow each step of the WiMAX Three- Phase Network Design process
• List eight WiMAX-specific network design considerations
• Model a flat-earth WiMAX network with the Design spreadsheet, and determine sensitivity of the estimated economic payback to changes in market and technical factors
• Determine site selection criteria
• Determine cell density required for a desired level of service, performance, and coverage.
• Choose backhaul options to support throughput requirements

Module 9: WiMAX Coverage and Performance Planning with modeling tools

• Employ a modeling tool to prepare an RF plan for your network in a three-part case study
• Illustrate the effect of frequency, power, terrain, clutter and CPE location on coverage
• Import terrain and clutter databases
• List options for accommodating system and subscriber growth

Module 10: Capacity Design, and Oversubscription

• Mathematically relate oversubscription and subscriber quality of service
• Validate vendor design rules for capacity planning

Wow.. what a wonderful training materials. But the most sophisticated is, we have an opportunity to get WiMAX Forum RF Engineer Certificate. I have to plan another saving to this Certification Ganbatte!

High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design.

In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbps to support packet-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even higher data transmission rates up to 20 Mbps. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.

Currently (2002) 3GPP is undertaking a feasibility study on high-speed downlink packet access.

In this post, I’ll try to share about my experience in Cellular Radio Network Optimization. This post consists of several subject that maybe useful to upgrade our knowledge and I well opened if there are questions relate to those subject. Please feel free to discuss with me, you can post it on comment or send email.

Why Optimization?

Below, I’ll mention optimization objectives generally,

• increasing network availability (deal with call performances, i.e., drop calls reduction to increase the access completion rates, handover control : assure enough handover to cover costumers mobility)
• increasing network quality (deal with speech and data quality to increase customer satisfaction)
• increasing network capacity (deal with capacity management efficiently, i.e., maintaining network resources to meet customer base needs so the blocking possibility is minimum)

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well… after we’ve talked about optimization aims, below we’ll discuss about optimization

procedures. First, we need to know how’s the network developmnt process takes place. After Radio Network Planning Process and network are being implemented, Radio Tuning (a.k.a basic radio optimization) and Radio Verification have to be done to assure that the network meet the operator needs. And, after Operator have accepted the network and network UP here we go..the (extended) Optimization process is begin.

Radio Optimization is done because several causes,

• systematics inacurracies (Tool database, prediction algorithms..)
• statistical processes involved (Radio Propagation, traffic..)
• Assumption made
• Human error (Planning errors, data entry, installation errors…)
• equipment faults (hardware and software)
• network growth

causes that mentioned above, could make network anomaly and it influence the customer satisfactions. So… from costumer complains statistics we know where and when does the
network unstability take a place. Hmm…is there any left behind?? yup… we have to know what, why, and how…We need The (extended) radio Optimization to answer thoose question’s left, so we can cure the network unstability ^_^

From the description above, we can conclude that Optimization process is devided into Basic Radio Optimization and Extended Radio Optimization. Both of them are controled by O&M(Operation and Maintenance). The main difference is that the Basic Radio Optimization will be done before network launch, and Extended Radio Optimization will be done after network is launched with normal subscriber.

2. Basic Radio Optimization (Radio Tuning)

System Tuning is done on this process, in order to meet the Operator requirements. The tuning activity have to change several cell paramaters, so the quality requirement is reached. On the high coverage and traffic demands areas usually this processes will be repeated a number of times untill the system reach Optimum performance.

3. Extended Radio Optimization

This process is done as customer complains follow-up. In the real network which is loaded by customer’s traffic, it often suffer several problems that effect the customer satisfaction. From customer complains statistics we can locate the network problem and when did it took a place. After we know where and when, the Optimization team will go to that spot and do tests measurement to take a log file and check the equipment conditions.
The tests measurement and equipment conditions data will be analyzed to make recommendation so the network problem can be fixed.

4. Tests Measurements

This activity is carried out with test mobile system (i.e., laptop with tests measurement software installed, Mobile station, and GPS for outdoor case) to record logfile that contains the signaling information send over the air interface and will consists following paramaters:

• Information for channel in use (serving cell):

BCCH
ARFCN
BSIC
TIMING ADVANCE
TX POWER (MS)
RX Qual
RX Lev

• Information for handover candidates (neighbors cell)

BCCH
BSIC
RxLev

note : on my projects, I use TEMS investigation 4 or above..

Hmm.. before we go to the next subject, we have to know the deffinition of paramaters which is mentioned above. ^_^

BCCH : Broadcast Control Channel is a key channel contains information about network configuration (network to MS direction) which is used for neighbouring cell measurements to determine cell reselections and handovers. BCCH allocation (BA) is a list of BCCH carriers in use within a specific geographical area of PLMN. It Indicates the RF Channels that the MS required to monitor while camped on a cell of that PLMN. BCCH term’s frequently used to refer to a carrier or a channel that often lead to confusion. Well on this case, it means carrier or channel.

ARFCN : Absolute radio frequency channel number. An identifier or number of a channel used on the Air-interface. From the ARFCN, it is possible to calculate the frequency of the uplink and the downlink that the channel uses.

BSIC :Base station identity code. An identifier for a BTS, although the BSIC does not uniquely identify a single BTS, since it has to be reused several times per PLMN. The purpose of the BSIC is to allow the mobile station to identify and distinguish among neighbor cells, even when neighbor cells use the same BCCH frequency. Because the

BSIC is broadcast within the synchronization channel (SCH) of a BTS, the mobile station does not even have to establish a connection to a BTS to retrieve the BSIC. It consists of the network color code (NCC), which identifies the PLMN, and the base station color code (BCC).

TA : Timing advance. The agreement in a GSM system is for the MS to send its data three time slots after it received the data from the BTS. The BTS then expects the bursts from the MS in a well-defined time frame. This prevents collision with data from other mobile stations. The mechanism works fine, as long as the distance between MS and BTS is rather small. Increasing distance requires taking into account the propagation delay of downlink bursts and uplink bursts. Consequently, the mobile station needs to transmit earlier than defined by the “three time slots delay” rule. The information about how much earlier a burst has to be sent is conveyed to the mobile station by the TA. The TA is dynamic and changes in time. Its current value is sent to the mobile station within the layer 1 header of each SACCH. In the opposite direction, the BTS sends the current value for TA within the MEAS_RES messages to the BSC (e.g., for handover consideration). The farther the MS is away from the BTS, the larger is the required TA. Using the TA allows the BTS to receive the bursts from a particular MS in the proper receiver window. The BTS calculates the first TA when receiving a RACH and reports the value to the BSC. TA can take any value between 0 and 63, which relates to a distance between 0 km and 35 km. The steps are about 550 m (35 km/63 » 550 m). With respect to time, the different values of TA refer to the interval 0 ms through 232 ms, in steps of 48/13 ms. It is important to note that this value of TA represents twice the propagation delay.

Tx Power (MS): Power transmited by Mobile Station

RxLev: RXLev provides the results of the measurement of the receiving level on the
Air-interface. These measurements are performed independently by the MS and the BTS. On this case RxLev is measured on the MS.

RxQual : RXQUAL values, are relevant for the decision of a BSC on power control and handover. They indicate the bit error rate that was measured on the Air-interface. The bit error rate can be determined by facilitating the training sequence. If you want to learn more… you can read the gsm recommendation

Measurements are to be taken on request from the analyzing team due to prioritizing form the coordinator. The data collection will partly consist of pure measurements and a pre analysis of the collected data.
Data collection can be divided in to three parts:
- continuous drive test (drive over an area to detect poor coverage, handover missed, interference..etc)
- spot drive test (dedicated measurement on specific problem spots for detail analyzing of particular problem)
- network performance test (typical measurements over a hugh area i.e., town or road distance, such as: Call Success Test, Quality level, etc.)

Should be noted that after each data collecting, the docummentation of data results must be regulated nicely, so on the post processing the analyze team can use that results easily.

well…if there’s no question, I’ll go to the next subject. :p

5. Measurement Analysis

The main goal of Optimization process is to improve the network performance. This is the list of analysis :
- signal strength (is checked according specified mobile classes inside actual coverage area)
- adjacent and cochannel interference
- handover pattern (to avoid “Ping Pong” handover)

The results of these analysis is Technical Recommendation wich is deal with action request for equipment config change both hardware (antenna configuration,etc.) and software (RF parameters).

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I think is enough for this post, I’m afraid it’s too theoretically :P. Hmm.. maybe on the next chapter.. I’ll post a little bit “practical”, about tools, about TEMS, about hardware, about post processing, etc. Just wait and see…

First I’d like to show you the network architecture that I filched from www.ccpu.com:

On the network architecture above, we can see 4G(3G LTE/SAE), 3G/3.5G HSPA, and IMS convergence. It should be noted that the picture above implement backward compatibility technology i.e., 3GPP IMT 2000 and IMT advanced.

We know, beside 3GPP there’s another technology such as 3GPP2 (based on CDMA2000 evolution and UMB) and also WiMAX. So… how we choose the interoperability scenario for this various technology?

Below I give another picture from www.telkom.info, so we can distinguish the differences

hmm… is there any left behind? yup, we haven’t talked about WiMAX Network architecture yet. So below I post another picture related to WiMAX architecture:

Well, after we know each network architecture, now we will begin to discuss about the interoperability or interworking between them.

First of all, we have to equalize our perception about network architecture. Commonly, we can divide the network architecture into three main parts, i.e., Radio Access Network, Transmission Network ( Transport) and Core Network.

Well, after we have same perception about network architecture, now we can focus on Radio Access Network which is experienced rapid development in this 5 past years.

Hmm… as mentioned on Wikipedia, 4G objectives are:

• A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site)
• High network capacity: more simultaneous users per cell,
• A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,
• A data rate of at least 100 Mbit/s between any two points in the world,

for the points above, let’s take a look this picture:

what can we see on the picture above is: all the evolution are using OFDMA!! so we can conclude that 4G technology are seems to be OFDMA and it’s evolution using MIMO, MISO, beamforming, etc. in order to achieves high network efficiency, high network capactiy, high data rate ( though less than 100 Mbps ). In other word: LTE, UMB, and WiMAX just like a brother and sister huh..

• Smooth handoff across heterogeneous networks,
• Seamless connectivity and global roaming across multiple networks,

for this two point above, I have my own opinion: All the network which is standardized by 3GPP and 3GPP2 are based on wide area concept ( GSM, CDMA, 3G UMTS, LTE, UMB). So how about the other network such as PAN, WLAN, which is based on small area concept?? How we can make those network interwork each other? As we know that on 4G beside horizontal handover ( intrasystem handover ), 4G system should have vertical handover capability ( intersystem handover ) to get the network access in harmony with user application QOS. So… we have to build a hybrid network which can adopt wide area concept and small area concept in to one system. The alternative solution is to have Software Defined Radio on the User Equipment. With this kind of technology, smooth handover across heterogeneous system and global roaming across multiple networks can be achieved :D.

• High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)
• Interoperability with existing wireless standards, and
• An all IP, packet switched network.

hmm.. now we are going to discuss about the three last points. Well, as we have discussed above the most rapidly development technology is on the Radio Access side. But don’t forget, on 4G we have to maintain QOS for various application, over IP end to end network, without ignoring the interoperability with the existing wireless standards. So… what should we do??

Thanks god.. we have IMS. Yup!! the IP Multimedia Subsystem. With this element on the core network, what ever the radio access technology as long as it use IP, IMS can handle it. And don’t forget IPv6 to address all of equipment in this world…hehehe…

btw…jd inget slogan makanan : “Apapun makanannya, minumnya teh Botol Sosr*!!”, mungkin dalam dunia telekomunikasi… bisa kita ubah slogan tersebut menjadi: “Apapun teknologi akses radionya…core networknya: IMS!! ”

Well… maybe sometimes I’ll make an article about IMS… (after I’ve learned about it…). Thanks for the attention…hope this article will be useful. I’m sorry if there’s a lot of mistakes.. and I well opened to discuss it

In this post, I wanna share with you about CDMA2000 Optimization Procedure. Hope you’ll enjoy it!

Wireless network Optimization can be devided in to three layers:

• Device Layer
• Network Layer
• Resource Utilization Layer

We can conduct some methods to examine problems on those layers, i.e.,

• Drive tests and Analysis
• Signaling Tracking
• OMC analysis
• Synthesis

Let’s we go in to deep to each layer above,

1. Device Layer
   • Antenna and Feeder Cable Fault
   • Transmission Fault
   • GPS Fault
   • Wireless Configuration
   • Office Direction Problem
   • Termination Problem
2. Network Layer
   • Solving Dropped Call Problem with Drive Test and Analysis Method
   • Solving Problem with OMC Analysis Method
   • Improving Coverage with Synthess Method
3. Resource Utilization Layer
   • Network Block Optimization
4. 
   

CDMA Performance Indicators

RF Performance indicators captured by drive-test activity. It show the CDMA RF environment to guide Optimization and Troubleshooting in air interface. Some parameters indicate uplink conditions, some downlink, and some both. These parameters collected at the subscriber side, so it’s easy to capture using commercial handset equipment without BSC’s assist.

Basic knowledge about CDMA spread spectrum signal characteristics such as: channel definitions, power control system, call processing flow, signal behaviour in noise and interference, and RF units ( transmitter and receiver) are needed, to analyse the parameters below.

• FER (Frame Error Rate) -> an excellent call quality summay statistic, it’s the end result of the whole transmission link
  • reverse channel -> realized on the Base Station
  • forward channel -> realized at handset
  • if FER is good, any other problems aren’t having much effect
  • if FER is bad, we have to check other indicators to analyze the network problem, because FER is just the end-result of the problem
• Mobile Receiver Power (Rx)-> Received Power at the handset (dBm). It should be noted that Received Power is Important, but it’s exact value isn’t critical.
  • High Rx value (-35 dBm or higher) could cause overload condition in Amplifier sensitivity, intermod and code distortion on received CDMA signals.
  • Low Rx value (-105 dBm or weaker would leave too much noise in the signal after de-spreading, resulting symbol errors, bit errors, bad FER and other problems.
• Ec/Io -> We can’t just use the handset’s power level to guide handoffs because it represents the total power measurement from all sectors reaching the handset. To measure the the signal level of each sector individually, we have to use each sector’s pilot (Walsh 0) as a test signal to guide handoffs.
  • Ec/Io is a parameter, represents pilot cleannesses.
  • foretells the readability of the associated traffic channels to guide soft handoffs decision
  • derived from: ratio of good to bad energy seen by search correlator at the desired PN offset -> Ec/Io(forward) = Pilot Energy / (Paging + Synch + Traffic) Energy. Can be degraded by strong RF from other Cells, Sectors (imperfect PN orthogonality could cause -20 dB degradation) and also by noise.
  • in Light condition (without traffic) Ec/Io = 3 dB, in Heavy loaded Ec/Io = -7 dB
  • in a clean Situation which theres a sector dominant, Ec/Io just as good as it was when transmitted. But in “Pilot Pollution” condition, mobile hears a ’soup’ made up of all the overlapped sectors signal. So Io is the sum of all the signal received by MS, and Eo is the energy of desired sector’s Pilot signal. The Large Io will overrides the weak Ec -> Ec/Io is too Low!
• Handset Transmitter power (TxPO)
  • TxPO is the actual RF power output of the handset transmitter(max= 23 dBm), including combined of open loop power control and closed loop power control (TxGA)
  • this is the simple formula : TxPO = -(Rx dBm) - C + TxGA ( C= +73 for 800 MHz systems, and C=+76 for 1900 MHz systems) to reach balance link.

Maybe enough for this post.. because I have a low battery condition now :P, and I forgot to bring may laptop’s charger…

Hope this post useful for us…