4G LTE KEY PERFORMANCE INDICATORS

Key performance indicators of KPI’s are indicators for if a device or equipment meets a certain relaibility criteria for being ready for deployment.

The KPI’s defined are:

1.    Accessibility

2.    Retainability

3.    Integrity

4.    Availability

5.    Mobility

Business level requirements: if an end user cannot access a service it is hard to charge for the service. Also, if it happens often that an end user cannot access the provided service, the end user might change wireless subscription provider i.e loss of income for the network operator.

Specification level requirements : the accessibility of an end-user application covers a wider area than just the UTRAN part. Hence it is important to realize that a KPI for this in E-UTRAN shall be limited to the parts that E-UTRAN has control of i.e the UTRAN KPI shall be defined so that it indicates the EUTRAN contribution to the end user impact.

There are certain tests to access the accessibilty KPI:

1.    RRC connection set up for registration success rates

2.    RRC connection set up for services success rates

3.    Initial E-RAB setup success rates

4.    Successive E-RAB setup success rates

5.    Call (VOIP) setup success rates

User case description : in providing end-user services to eireless end users , the first step is to get access to the wireless service. First after access to the service has beeb performed , the service can be used. If an accessibility measurement is not considered Ok,then the network operator can investigate which steps that are required to improve the accessibilty towards their customers.

PROTOCOL SIGNALING PROCEDURES IN LTE

PROTOCOL SIGNALING PROCEDURES IN LTE

Overview:  the ever increasing growth of the internet and services has the need of more and more bandwidth. LTE promises higher data rates. 100 mbps in the downlink and 50 mbps in the uplink in LTE’s first phase it support scalable bandwidth from 1.25 mhz to 20 mhz.

Network architecture:

The architecture of LTE network is given with the various interfaces between the network elements. The functions of various elements are:

eNode:  radio resource management functions , IP header compression, encryption of user data streams, selection of an MME and transmission of paging message.

MME: it provides handovers , authentication and bearer management.

S-GW: the local anchor point of inter-eNode handover, accounting on user.

P-GW: UE IP address allocation , packet filtering , gating and rate enforcement.

BEARERS in LTE:

In LTE, end to end bearers are realized by the EPS bearers which are a collection of radio, S1 and S5/S8 bearers. An EPS bearer identify uniquely an EPS bearer for one UE accessing via E-UTRAN .

There are three kinds of bearer in LTE: radio bearers, S1 bearers and EPS bearers. In the UE, the uplink maps a traffic flow aggregate to an EPS bearer in the uplink direction and in PGW the downlink TFT maps a traffic flow aggregate to an EPS bearer in the downlink.

Radio bearer: a radio bearer transports the packets of an EPS bearer between the UE and eNode B.

S1 bearer: an S1  bearer transports the packets of an EPS bearer between an eNodeB and a S-GW.

S5/S8 bearer : it transports the packets of an EPS bearer between the S-GW and PDN GW.

SYSTEM INFORMATION BROADCASTING:
 to get service from the network , UE has to select the network a UE has to select the network and camp on a cell. For this to happen , the UE has to synchronize itself with the network at the frame and slot level. The network broadcasts this information to help the UEs in their selection process.

RANDOM ACCESS PROCEDURE—SYSTEM ACCESS

The UE can utilize the services of the network once it is synchronised in both the downlink as well as uplink direction. After the PLMN and cell selection the UE is synchronised with the network in the uplink direction. The random access procedure over PRACH is performed by the UE for this purpose. There are two types of RAPs:

Contention based Random Access Procedure: in this mode multiple UEs may attempt to access the network at the same time, thereby resulting in collisions.

Non- contention based Random access procedure : the network initiates this procedure in case of a handover of a UE from one eNode to another in order to keep handover latency under control. There are no collisions with other UE’s because the eNode controls the procedure

RESOURCE ALLOCATION AND MODULATION TECHNIQUES

RESOURCE ALLOCATION

It is assigning the available resources in an economic way. It is a part of resource management. This allocation is done by strategic planning in which resorce allocation is a plan for using available resources e.g human resources to achieve gaols in future. In computing it is necessary for any application to be run on the system. When the user opens any program this will counted as a process and therefore requires the computer to allocate certain resources for it to be able to run. Such resources could be memory, files etc.

ORTHOGONALITY

In communications, multiple access schemes are orthogonal when an ideal receiver can completely reject strong unwanted signals from the desired signal using different basis functions. E.g TDMA where the orthogonal basis functions are time slots.

MODULATION

It is the process of varying one or more properties of a periodic waveform called the carrier signal with the modulating signal which contains the information to be transmitted.e.g a digital bit stream or an analog audio signal inside another signal that can be physically transmitted. Modulation of a sine waveform is used to transform a baseband message signal into a passband signal.the device which perform modulation is called modulator and the device which performs demodulation is called demodulator.

Modulation is of two types:

1.   Analog modulation

2.   Digital modulation

Analog modulation : the main aim of this is to transfer an analog baseband which could be audio signal or TV signal over an analog bandpass channel at a different frequency.

Digital modulation : the main aim of this is to transfer a digital bit stream over an analog bandpass channel e.g PSTN

Analog and digital modulation facilitate frequency division multiplexing (FDM), where several low pass information signals are transferred simultaneously over the same shared physical medium, using separate passband channels (several different carrier frequencies).

The aim of digital baseband modulation methods, also known as line coding , is to transfer a digital bit stream over a baseband channel, typically a non-filtered copper wire such as a serial bus  or a wired local area network.

The aim of pulse modulation methods is to transfer a narrowband analog signal, for example a phone call over a wideband  baseband channel or, in some of the schemes, as a bit stream over another digital transmission system.

In music synthesizers, modulation may be used to synthesise waveforms with an extensive overtone spectrum using a small number of oscillators. In this case the carrier frequency is typically in the same order or much lower than the modulating waveform.

In analog modulation, the modulation is applied continuously in response to the analog information signal. Common analog modulation techniques are:

·       Amplitude modulation(AM) (here the amplitude of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal)

Double-sideband modulation (DSB)

Double-sideband modulation with carrier (DSB-WC) (used on the AM radio broadcasting band)

Double sideband suppressed carrier transmission (DSB-SC)

Double sideband reduced carrier transmission (DSB-RC)

      Single sideband modulation (SSB, or SSB-AM)

SSB with carrier (SSB-WC)

SSB suppressed carrier modulation (SSB-SC)

Vestigial sideband modulation (VSB, or VSB-AM)

Quadrature amplitude modulation (QAM)        

    Angle modulation, which is approximately constant envelope

Frequency modulation (FM) (here the frequency of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal)

Phase modulation (PM) (here the phase shift of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal)

In digital modulation, an analog carrier signal is modulated by a discrete signal. Digital modulation methods can be considered as digital-to-analog conversion, and the corresponding demodulation or detection as analog-to-digital conversion. The changes in the carrier signal are chosen from a finite number of M alternative symbols.

Schematic of 4 baud (8 bit/s) data link containing arbitrarily chosen values.

A simple example: A telephone line is designed for transferring audible sounds, for example tones, and not digital bits (zeros and ones). Computers may however communicate over a telephone line by means of modems, which are representing the digital bits by tones, called symbols. If there are four alternative symbols (corresponding to a musical instrument that can generate four different tones, one at a time), the first symbol may represent the bit sequence 00, the second 01, the third 10 and the fourth 11. If the modem plays a melody consisting of 1000 tones per second, the symbol rate is 1000 symbols/second, or baud. Since each tone (i.e., symbol) represents a message consisting of two digital bits in this example, the bitrate is twice the symbol rate, i.e. 2000 bits per second. This is similar to the technique used by dialup modems as opposed to DSL modems.

According to one definition of digital signal, the modulated signal is a digital signal, and according to another definition, the modulation is a form of digital to analog conversion. Most textbooks would consider digital modulation schemes as a form of digital transmission, synonymous to datatransmission; very few would consider it as analog transmission.

OFDM TRANSMITTER AND RECEIVER

                          OFDM TRANSMITTER        

An OFDM carrier signal is the sum of a number of orthogonal sub-carriers, with baseband data on each sub-carrier. These sub-carriers are being independently modulated commonly using some type of modulation technique may be  Quadrature amplitude modulation (QAM) or phase shift keying (PSK). This  baseband signal is typically used to modulate a main RF carrier.

 is a serial stream of binary digits. By inverse multiplexing , these are first demultiplexed into  parallel streams, and each one mapped to a  symbol stream using some modulation technique.  The modulation techniques may be different, so some streams may carry a higher bit-rate than others.

An inverse FFT is computed on each set of symbols, giving a set of complex time-domain samples. These samples are then quadrature mixed to passband in the standard way. The real and imaginary components are first converted to the analogue domain using DACs ; the analogue signals are then used to modulate cosine and sine waves at the carrier  frequency, , respectively. These signals are then summed to give the transmission signal, 

                     OFDM RECEIVER

The receiver picks up the signal  , which is then quadrature-mixed down to baseband using cosine and sine waves at the carrier frequency. This also creates signals centered  on , so low-pass filters are used to reject these. The baseband signals are then sampled and digitised using ADCs , and a forward FFT is used to convert back to the frequency domain.

This returns  parallel streams, each of which is converted to a binary stream using an appropriate symbol detector. These streams are then re-combined into a serial stream ,  , which is an estimate of the original binary stream at the transmitter.

                             

USAGE:

OFDM is used in ADSL connections that follow the ITU G.992.1 standard, in which existing copper wires are used to achieve high-speed data connections.

Long copper wires suffer from attenuation at high frequencies. The fact that OFDM can cope with this frequency selective attenuation and with narrow-band interference are the main reasons it is frequently used in applications such as ADSL modems. However, DSL cannot be used on every copper pair; interference may become significant if more than 25% of phone lines coming into a central office are used for DSL.

 OFDM is exclusively used in LAN and MAN applications.           

FOURIER TRANSFORM

The fourier transform, named after JOSEPH FOURIER is a mathematical transform with many applications in physics and engineering. It transforms a mathematical function of time f(t) into a new function sometimes denoted by F. which is frequency and measured in radions per second . the new function is called fourier transform.the term “Fourier transform” refers to both the transform operation and to the complex value function it produces. In case of a periodic function the fourier transform can be simplified to tha calculation of a discrete set of complex altitudes called fourier series coefficients. It is possible to recreate a version of the original fourier transform known as discrete time Fourier transform.

 The fourier transform comes from the study of Fourier series. In the study of fourier series complicated but periodic functions are written as the sum of simple waves mathematically represented by sines and cosines. Due to the properties os sine and cosine it is possible to recover the amplitude of each wave in a fourier series using an integral. In some cese it is desirable to use Euler’s formula  e^2πiθ= cos(2πθ) +isin(2πθ) . the usual interpretation of this complex number is that it gives both the amplitude of the wave present in the function and the phase of the wave.

 There is a  close  connection  between the  definition of  Fourier  series and the Fourier transform  for  functions  f  which are zero  outside of  an interval. For  such a function, we can calculate its Fourier series on any interval that includes the points where f is not identically zero. The Fourier transform is also defined for such a function. As we increase the length of the interval on which we calculate the Fourier series, then the Fourier series coefficients begin to look like the Fourier transform and the sum of the Fourier series of fbegins to look like the inverse Fourier transform.

RADIO RESOURCE MANAGEMENT

It is the level control of interference and the other characteristics in wireless communication systems , e.g cellular networks, wireless and broadcasting systems. It involves algorithms for controlling parameters such as transmit power, user allocation , data rates, handover criteria and error coding scheme etc. it concerns multi-user and multi cell network capacity issues rather than point to point channel capacity.  In traditional telecommunications research and education it uses channel coding and source coding with a single user in mind although it may not be possible to achieve the maximum channel capacity when several users and adjacent base stations share the same frequency channel.  RRM is especially important in systems limited by co-channel interference rather than by noise, for example cellular systems and broadcast networks homogeneously covering large areas, and wireless networks consisting of many adjacent access points that may reuse the same channel frequencies.

The cost for deploying a wireless network is normally dominated by base station sites (real estate costs, planning, maintenance, distribution network, energy, etc.) and sometimes also by frequency license fees. The objective of radio resource management is therefore typically to maximize the system spectral efficiency in bits/sec, that the grade of service should be above a certain level. The latter involves covering a certain area and avoiding outage due to co-channel interference, noise, attenuation caused by path losses, fading caused by shadowing and multipath, Doppler shift and other forms of distortion. The grade of service is also affected by blocking due to admission control or inability to guarantee quality of service that is requested by the users.

Static RRM involves manual as well as computer-aided fixed cell planning or radio network planning. E.g:

1.     Frequency allocation band plan

2.     Antenna heights

3.     Antenna directions

4.     Modulation and coding parameters

5.     Antenna space diversity.

Dynamic RRM schemes adjust the radio parameters to tha traffic load, user mobility, quality of service requirements etc.e.g:

1.     Power contraol algorithms

2.     Link adaption algorithms

3.     Dynamic channel allocation.

 

INTER-CELL RRM:

Networks like LTE standard are designed for a frequency reuse of one. Thus neighbouring cells use the same frequency spectrum.such standards exploits Space Division Multile Access and can be highly efficient but requires close coordination between cells to avoid intercell interference. Intercell RRM coordinates resourse allocation between different cell sites by using MIMO techniques.

S/MIME (Secure/multipurpose Internet Mail Extensions)

It is a standard for public key encryption and signing of MIME data. s/mime is on an IETF standards track and defined in number of documents. It was originally developed by RSA data security inc. S/MIME provides the cryptographic security services for electronic messaging applications e.g authentication, message integrity, privacy and data security.S/MIME specifies the MIME type for dta enveloping which means encryption.MIME entity to be enveloped is encrypted and packed into an object which subsequently is inserted into an application MIME entity.

Before S/MIME can be used in any of the above applications one must obtain and install an individual key/certificate either from one’s in house certificate authority or from a public CA.  Encryption requires having the destination party's certificate on store (which is typically automatic upon receiving a message from the party with a valid signing certificate).  While it is technically possible to send a message encrypted (using the destination party certificate) without having one's own certificate to digitally sign, in practice, the S/MIME clients will require you to install your own certificate before they allow encrypting to others.   

Depending on the policy of the CA, the certificate and all its contents may be posted publicly for reference and verification. This makes the name and email address available for all to see and possibly search for.

 Other CAs only post serial numbers and revocation status, which does not include any of the personal information. The latter, at a minimum, is mandatory to uphold the integrity. Even more generally, any message that an S/MIME email client stores encrypted cannot be decrypted if the applicable key pair's private key is unavailable or otherwise unusable (e.g., the certificate has been deleted or lost or the private key's password has been forgotten). Note, however, that an expired, revoked, or untrusted certificate will remain usable for cryptographic purposes. In addition, indexing of encrypted messages'clear text may not be possible with all email clients. Regardless, neither of these potential dilemmas is specific to S/MIME but rather cipher text in general and do not apply to S/MIME messages that are only signed and not encrypted.

The 3GPP all IP architecture - DiffServ-Based Architecture

The 3GPP all IP architecture relies on mobile IP (MIP) infrastructure for roaming between different access gateways. Thus, MIP home agent and foreign agent are introduced in reference architecture.A wireless IP network consist of two components: a wireless access network and a fixed corenetwork. There are important issues that should be addressed in wireless IP networks in order toprovide a seamless service in both fixed and mobile environments. Perhaps the most challenging issue is resource management and quality of service provisioning. This is even more difficult considering that there is no native resource management or quality of service control function in traditional IP networks. Current wired IP only offers the best effort service model which treats all packets from all users equally. In wireless environments due to specific characteristics of wireless channel, QoS provisioning is even more challenging. Furthermore, each wireless access network, has potentially its own wireless technology and administrative policies which makes it more difficult to have a uniform resource management mechanism. The goal of this section is to discuss resource management architectures for integrating different wireless networks in order to provide seamless connectivity. The proposed architectures adopt IP as the common network layer protocol. To minimize the amount of change inside the network, we use the existing resource management mechanisms proposed for IP networks as much as possible. In all proposed architectures, the core network is based on the Diffserv model.

DiffServ-Based Architecture

In DiffServ-Based architecture, not only the core network is DiffServ-capable but also the access networks are DiffServ-capable. In this architecture acellular network overlaid by DiffServ domains operates as the radio access network.In the previous subsection, we discussed how the static nature of DiffServ can degrade the radio resource utilization in wireless access networks. Therefore, a more fine-grained architecture based on IntServ was proposed. It was also mentioned that because of limited radio resources, the number of flows and consequently the amount of state information required for IntServ/RSVP7 operation is quite reasonable with respect to the scalability requirement. These assumptions are reasonable for low-bandwidth systems, e.g. a 3G networks. However, when the access network operates on a high-bandwidth IP-based wireless technology, e.g. a wireless LAN, these assumptions do not stand for the following reasons: Typically, such technologies have high capacities in order of several Mbps. Therefore, it is possible to have a large number of flows simultaneously in the network. Considering that future cellular technologies such as 4G will expand the available radio resources to the same orders, then this will be problematic even in those environments.

• Due to the inherent IP-based architecture of these technologies, traffic flows have different characteristics and requirements than those in conventional cellular networks. The applications intended for such environments are delay-tolerant and do not require strict QoS guarantees (web browsing compared to voice calls for instance). Also, their generated traffic is bursty in nature and hence it is difficult to describe their bandwidth requirements accurately a priori. The types of applications supported by conventional cellular networks are limited which facilitate the classification of their requirements. This is not true in wireless LAN environments.

• Mobility patterns are different in WLAN-based hot spot environments compared to those in conventional cellular networks. Hot spot traffic is more chaotic and hence more difficult to predict. As a result, it is not possible in practice to reserve appropriate amount of resources beforehand for each individual connection which may handoff to the hot spot.In contrast, traffic aggregates are usually more smooth and predictable thanks to the law of large numbers. This suggest that class-based resource management is more feasible in wireless environments.

• The wireless environment is rapidly changing. Wireless channel capacity fluctuates over time with interferences. So, it is difficult to achieve strict QoS guarantees similar to those in wireline networks with fairly stable channel quality. In this case coarse grained QoS guarantees like those offered by DiffServ are sufficient and in fact more appropriate for the target application types. For all above reasons we believe that the DSB architecture is a more appropriate candidate for future all-IP wireless networks than the ISB architecture.

All IP cellular networks - Mobile Wireless Internet Forum MWIF, 3GPP, IETF

There are several organisations developing specifications for "All IP" cellular networks; i.e., fully IP protocols based networks. The specification work is on going in established standard developing organisations such as 3GPP, 3GPP2, and IETF, as well as in different industry forums such as 3G.IP and MWIF. Currently there are several ongoing efforts to define cellular network architectures that would enable fully IP based service delivery  i.e. not only data, but also speech service would be provisioned over IP bearer. Such network architectures are usually referred as All IP networks.

 3G.IP -- 3G.IP is an operator-driven initiative, which "actively promote a common IP based wireless system third generation mobile communications technology" as stated in forum's mission statement . The 3G.IP has defined reference architecture for All IP network architecture based on evolution of UMTS. 

Mobile Wireless Internet Forum (MWIF). MWIF is another operator-driven industry association, which "drive acceptance and adoption of a single mobile wireless and Internet architecture" as stated in the MWIF . The MWIF has specified an access independent All IP network architecture.

3 ^rd Generation Partnership Project (3GPP). 3GPP is a global SDO that was formed between Chinese, European, Japanese, Korean, and North American national SDOs to specify GSM based 3^rd Generation cellular system, often referred as UMTS. Currently 3GPP is working on UMTS evolution to All IP network. The All IP specifications will be part of 3GPP Release 5.

  

Internet Engineering Taskforce (IETF). IETF is community of people "concerned with the evolution of the Internet architecture and the smooth operation of the Internet" as defined in IETF . IETF is not actually concerned All IP architectures as such, but is has specified and is assumed to specify, several protocols that will be essential for All IP networks.

                                                  ARCHITECTURE PROPOSALS

We describe the All IP network architecture proposals on table in 3GPP, 3GPP2, and MWIF. The reader should note that the work is still on going in all these forums. Thus, the architectures presented here are subject to change before the specifications are completed.

The Databases in 3GPP architecture are condensed into Home Subscriber Server (HSS). The HSS has two distinct functions: Home Location Register (HLR) and User Mobility Server (UMS). The former is equivalent of the HLR in 3GPP Release 99 (UMTS) specifications, which holds subscriber profile information needed in GPRS part of the network. The latter stores subscriber profiles required in the IPT core network.