4G, Long Term Evolution (LTE), VOLTE and VOWifi

LTE stands for Long Term Evolution and is a registered trademark owned by ETSI (European Telecommunications Standards Institute) for the wireless data communications technology and a development of the GSM/UMTS standards.

  • Both radio and core network evolution
  • All-IP packet-switched architecture
  • standardised by 3GPP
  • lower CAPEX ans OPEX involved

LTE evolved from an earlier 3GPP system known as the Universal Mobile Telecommunication System (UMTS), which in turn evolved from the Global System for Mobile Communications (GSM). Also it is aligned with 4G (fourth-generation mobile)

It is backward compatible with GSM/EDGE/UMTS/CDMA/WCDMA systems on existing 2G and 3G spectrum, even hand-over and roaming to existing mobile networks.

Motivation for evolution – Wireless/cellular technology standards are constantly evolving for better efficiency and performance.LTE evolved as a result of rapid increase of mobile data usage. Applications such as voice over IP (VOIP), streaming multimedia, videoconferencing , cellular modemetc.

It provides packet-switched traffic with seamless mobility and higher qos than predecessors. Also high data rate, throughput, low latency and packet optimized radioaccess technology on flexible bandwidth deployments.

Timeline of Evolution 

  • GSM  : calls  on circuit switching ( CS ) between 2 parties for communication. Dedicated circuits are used for voice and SMS.
  • GPRS : packet switching (PS) is introduced for data services
  • UMTS / 3G : network elements begin evolving into PS . No changes to core.
  • EPC / LTE/VOLTE : No circuit switched domain at all .

Performance

Peak Data Rate

  • uplink – 75Mbps(20MHz bandwidth)
  • downlink – 150 Mbps(UE Category 4, 2×2 MIMO, 20MHz bandwidth) , 300 Mbps(UE category 5, 4×4 MIMO, 20MHz bandwidth)

Carrier bandwidth

Range from 1.4 MHz up to 20 MHz. Ultimately bandwidth used by carrier depends on frequency band and the amount of spectrum available with a network operator

Mobility 350 km/h

Multiple Access Schemes

  • uplink: SC-FDMA (Single Carrier Frequency Division Multiple Access) 50Mbps+ (20MHz spectrum)
  • downlink: OFDM (Orthogonal Frequency Division Multiple Access) 100Mbps+ (20MHz spectrum)
  • Multi-Antenna Technology , Multi-user collaborative MIMO for Uplink and TxAA, spatial multiplexing, CDD ,max 4×4 array for downlink

Coverage

  • 5 – 100km with slight degradation after 30km
  • LTE architecture supports hard QoS and guaranteed bit rate (GBR) for radio bearers.

Technology

All interfaces between network nodes are IP based
Duplexing – Time Division Duplex (TDD) , Frequency Division Duplex (FDD) and half duplex FD

MIMO ( Multiple Input Multiple Output ) transmissions –

Allows the base station to transmit several data streams over the same carrier simultaneously.
Modulation Schemes

QPSK, 16QAM, 64QAM(optional)

LTE Architecture

Primarily composed of

User Equipment (UE)

  • Mobile Termination (MT)
  • Terminal Equipment (TE) 
  • Universal Integrated Circuit Card (UICC) : also known as the SIM card for LTE equipments. It runs an application known as the Universal Subscriber Identity Module (USIM).

2. Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)

handles the radio communications between the mobile and the evolved packet core. High level representation for  eNodeB or eNB

Role of eNB : sends and receives radio transmissions to all the mobiles using the analogue and digital signal processing functions of the LTE air interface. eNB also controls the low-level operation of all its mobiles, by sending them signalling messages such as handover commands.

3. Evolved Packet Core (EPC)

This sub system resembles IMS environment.

Packet Data Network (PDN) Gateway (P-GW) communicates with the outside world simillar to GGSN ( GPRS support node ) and SGSN ( serving GPRS support node ) in UMTS and GSM.

Home Subscriber Server (HSS) is a central database that contains information about all the network operator’s subscribers. Almost simillar to HLR/AAA in 2G /3G architcture.

Mobility management entity (MME) controls the high-level operation

For a roming user in Visited-PLMN , he is connected with the E-UTRAN, MME and S-GW of the visited LTE network. However, LTE/SAE allows the P-GW of either the visited or the home network to be used, as shown in below:

For roaming prepaid charging , accounting flows are made to access prepaid customer data, via P-Gateways or CSCF in an IMS environment.

LTE-Advanced

LTE devices capable of CAT6 speeds (Category 6 )
Increased peak data rate – downlink 3 Gbps, Uplink 1.5 Gbps ( 1 Gbps = 1000 Mbps)
Spectral efficiency from 16bps/Hz in R8 to 30 bps/Hz in R10
Carrier Aggregation (CA)
Enhanced use of multi-antenna techniques
Support for Relay Nodes (RN)

References

Read More

Also read about previous generations of telecom namely 2 G and 3G

2G to 3G – generation of telecom

Where 2G is referred to as the GSM era , 2.5 G as the GPRS with GSM era. As compared to its predecessor 1G which used FDMA ( Frequency Division Multiplexing ) for channelization , 2G used used TDMA and CDMA for dividing the channels .