1. Cellular
Communication
Systems
***The Inside Story

2. Contents
Main Issues (Resources,
Capacity, Access, etc.)
Concepts Of Wireless
Communication
2G, 3G, LTE Topologies
DC-HSPA

4. Contents
Main Issues (Resources,
Capacity, Access, etc.)
Concepts Of Wireless
Communication
2G, 3G, LTE Topologies
DC-HSPA

6. Main Issues (Resources,
Capacity, Access, etc.)
Two main issues in cellular communication: multiple
access and interference management
Addresses how the overall resource (time, frequency and
space) of the system is shared by the users in the same cell
(intra-cell)
Addresses the interference caused by simultaneous signal
transmissions in different cells (inter-cell)
Multiple Access
Interference
Management

7. Main Issues (Resources,
Capacity, Access, etc.)
In addition, there is also an issue of how the resource is
allocated between the uplink (the reverse link) and the
downlink (the forward link). DUPLEXING
Time Division Duplex:
separates the transmissions in time
Frequency Division Duplex:
separates the transmissions in frequency
TDD
FDD

8. Main Issues (Resources,
Capacity, Access, etc.)
A cellular network provides coverage of the entire area by
dividing it into cells.

10. Contents
Main Issues (Resources,
Capacity, Access, etc.)
Concepts Of Wireless
Communication
2G, 3G, LTE Topologies
DC-HSPA

11. Frequency Reuse
Concepts Of Wireless
Communication
Intelligent allocation and reuse of channels throughout a
coverage region.
A set of radio channels for each base station, cell.
Adjacent cells: completely different channels
Same group of channels may be used to cover different cells
that are separated from one another to keep interference
levels within tolerable limits

12. When a mobile moves into a different cell while a
conversation is in progress, the call is transferred to a new
channel belonging to the new base station.
Points To Consider:
A. Hard handover VS. Soft handovers
Handovers
Concepts Of Wireless
Communication

13. Interference and System Capacity
A major limiting Factor
Concepts Of Wireless
Communication
Sources : mobile in the same cell, a call in progress in a
neighboring cell, or other base stations operating in the
same frequency band.
A. Co-channel Interference
B. Adjacent Channel Interference

14. Improving Coverage and Capacity in Cellular Systems
Demand goes up
The number of channels insufficient.
Design techniques to provide more.
Cell splitting and sectoring.
Concepts Of Wireless
Communication

15. Cell Splitting
Concepts Of Wireless
Communication
Cell splitting is the process of subdividing a congested cell into
smaller cells

16. Cell Sectoring
Dividing a cell into three (or six) equal-space sectors using
directional antennas.
The channels used in a particular cell are broken down into
sectored groups and are used only within a particular sector
Increasing the frequency reuse.
Concepts Of Wireless
Communication

17. Repeaters for Range Extension
Concepts Of Wireless
Communication
Hard-to-reach areas: within buildings, or in valleys or tunnels.
Radio re-transmitters, known as repeaters, are often used to
provide such range extension capabilities.

18. MULTIPLE ACCESS TECHNIQUES

19. Multiple Access
Allow many mobile users to share simultaneously a finite
amount of radio spectrum.
Mobiles are Mobile ---- No easy way ---- More penetration ----
More valuable is the spectrum ---- Role Of Multiple Access
Points To Consider:
A. Duplexing
B. High capacity is required.
C. NO severe degradation in the performance.

20. Three major techniques:
A. Frequency division multiple access (FDMA)
B. Time division multiple access (TDMA)
C. Code division multiple access (CDMA)
Others:
A. Orthogonal Frequency Division Multiple Access (OFDM)
Techniques
Multiple Access

23. Contents
Main Issues (Resources,
Capacity, Access, etc.)
Concepts Of Wireless
Communication
2G, 3G, LTE Topologies
DC-HSPA

24. 2G -GSM
The GSM network can be divided into following broad parts:
** The Mobile Station (MS)
** The Base Station Subsystem (BSS)
** The Network Switching Subsystem (NSS)

26. First Introduction Of DATA….
Same network + some changes
GPRS
Mobile Station (MS)
New Mobile Station is required to access GPRS services. These
new terminals will be backward compatible with GSM for voice
calls.
GPRS Support Nodes (GSNs)
Installation of new core network elements : the serving GPRS
support node (SGSN) and gateway GPRS support node (GGSN).
The BTS, BSC, HLR, VLR needed only software upgrades.

27. SGSN = Serving GPRS Support Node,
GGSN = Gateway GPRS Support Node,
and
GR = GPRS Register.

28. Migrating from GSM/GPRS to UMTS
3G -UMTS
From a GSM/GPRS network, the following network elements
can be reused:
(HLR) --- (VLR) --- (EIR) --- (MSC) --- (AUC) --- (SGSN) --- (GGSN)
From a GSM/GPRS communication radio network, the
following elements cannot be reused:
Base station controller (BSC)
Base transceiver station (BTS)
**Remain, Dual network operation, 2G/3G co-exist

29. 3G -UMTS
Migrating from GSM/GPRS to UMTS … Cont’d
The UMTS network introduces new network elements that
function as specified by 3GPP:
NODE B : WCDMA--- Frequency use (the whole network can
use a single frequency pair)/ Power requirements.
Radio Network Controller (RNC) : mainly control the NODE Bs
and their power levels.

31. The Quest For More:
More Spectrum
More Capacity
More Small Cells
More Speed (D&U)
More Business Solutions
More Consistency
And Less COSTS
More Users
More Market
Penetration
And Less COSTS

32. Peak download rates up 300 Mbit/s and upload rates up to
75 Mbit/s
MIMO (with 2×2 / 4×4 antennas using up to 20 MHz of
spectrum).
The LTE standard supports only packet switching with its all-IP
network --- Global Roaming
Improves call set-up time.
Higher data-carrying capacity and a higher spectral efficiency.
Lowers the cost-per-bit.
Increase the efficiency of entire network.
Operations easier and less expensive to manage.
WHY
LTE

34. LTE
LTE’s Radio Access Network (EUTRAN) : Evolved UMTS
Terrestrial Radio Access
It uses OFDMA radio-access for the downlink and SC-FDMA on
the uplink
EUTRAN consists only of ENODEBs on the network side.
The ENODEB performs tasks similar to those performed by
the NODEBs and RNC (radio network controller) together in
UTRAN.
The aim of this simplification is to reduce the latency of all
radio interface operations.

35. Evolved Packet Core Network
LTE
* Flat architecture, avoid protocol conversion.
* Separate the user data and the signaling

36. Very basic architecture of the EPS
LTE EPS
LTE

38. Contents
Main Issues (Resources,
Capacity, Access, etc.)
Concepts Of Wireless
Communication
2G, 3G, LTE Topologies
DC-HSPA

39. HSPA+: Building upon the solid global foundation
547HSPA NETWORKS IN 205 COUNTRIES
363HSPA+ NETWORKS IN 157 COUNTRIES
160DUAL-CARRIER NETWORKS IN 83 COUNTRIES
Source: www.gsacom.com , Feb 2014 3

40. 9
HSPA+ Dual-carrier is main-stream
Supporting 42 Mbps downlink peak data rate
Deployment of 42 Mbps
DC-HSPA+ technology
continues as the major
trend in 2014
– GSA, Mar 2014
160
NETWORKS
83
COUNTRIES
Countries launched/committed to Dual-carrier
Source: www.gsacom.com , Feb 2014

41. DUAL CARRIER-HSDPA
How It Works
HSPA & WCDMA : A True Success
Enhancements and new features : HSPA+, 3GPP rel.
8 to 10
Data rates .. Spectral efficiency .. Latency in the
system

42. How It Works
DUAL CARRIER-HSDPA
HSPA Additional Channels:
WHY: Provide the additional data capacity, the
control required.
In addition to the existing 3G UMTS channels.

43. How It Works
DUAL CARRIER-HSDPA
High Speed Downlink Shared Channel, HS-DSCH
** Data transport channel.
High Speed Signaling Control Channel, HS-SCCH
** Control Channel: Carries elements of info.
** Signal the scheduling to the users.
High Speed Dedicated Physical Control Channel,
HS-DPCCH
** Feedback to the scheduler.
** Located in the UL.

44. How It Works
SO How It Works
Carrier Aggregation
** 2 Engines in one car, driving with doubled rate
in the DL.
** DC-HSPA: Two adjacent DL carriers (5 MHz) +
one UL .. Peak rates D: 42 Mbps
** Scheduling and coordination:
-NODEB’s Scheduler.
-One HS-SCCH for each 5 MHz carrier.
-Decisions based on CQI (Channel quality info.)
feedback.

47. 10
Dual-carrier – Delivering high data rates in real networks
>5Mbps >50%
0 – 0.25Mbps
8.6%
15 – 20Mbps
14.1%
12.5 – 15Mbps
10.6%
10 – 12.5Mbps
8.7%
7.5 – 10Mbps
Source: Signals Research Group
0.25 – 0.5Mbps
Signals Ahead, September 2011, “The Mother of all Network Benchmark Tests”
4.8%
0.5 – 1Mbps
8.1%
1 – 1.5Mbps
6.5%
1.5 – 2Mbps
4.6%
2 – 2.5Mbps
3.8%
2.5 – 5Mbps
11.4% 5 – 7.5Mbps
9.9%
8.8%
USER DATA RATE OF THE TIME
>1Mbps ~80%
USER DATA RATE OF THE TIME
Based on comprehensive benchmarking tests conducted across two
operators in greater Dallas area (Texas), covering more than 23 miles of
driving, downloading nearly 7GB of data

49. Thanks
For
Listening

50. BIBLIOGRAHY:
• ITU (International Telecommunication
Union)
• Ericsson, QUALCOMM, and Alcatel-
Lucent White Papers.
• The 3rd Generation Partnership Project
(3GPP) Releases.
• Rohde-Schwarz
• Radio-Electronics.com