Broadband Radio Access Networks Challenges Prof. Hamid Aghvami Centre for Telecommunications Research- King’s College London
Broadband Radio Access Networks
Challenges
Prof. Hamid Aghvami
Centre for Telecommunications Research- King’s College London
Emerging candidates for next generation broadband radio
networks (4G?)
• 3GPP LTE
• 3GPP2 Ultra Mobile Broadband (UMB)
• Mobile WiMAX
Common features among them:
• OFDM-based air interface
• Adaptive modulation and coding
• Hybrid ARQ
• Fast scheduling
• MIMO and beam forming antennas.
• IP-based access network
NAP: Network Access Provider
ASN: Access Service Network
CSN: Connectivity Service Network
ASP: Application Service Provider
NSP: Network Service Provider
Source: WiMAX Forum
WiMAX Network Reference Model (NRM)
IP Based WiMAX Network Architecture
An open issue is:
How to split the radio resource and mobility management functionalities
between the BS and ASN GW.
Wireless Access Network Design
(In the context of end-to-end networking)
In the context of end-to-end networking ?
• End-to-end QoS
• End-to-end security
• End-to-end seamless mobility
Three main functionality groups of a wireless access network are:
- Mobility management
- QoS
- Security
Mobility Management
• The mobility management of a wireless access network includes how to solve
the problems of local seamless handover, idle mode and paging, and of course
the routing capabilities within the access network that allow these to take place
without constant address reassignment.
• All of these, especially the last, have major impacts on the internal architecture
of the access network, in terms of location of functionality in different network
elements.
QoS
• The problems are:
- How to identify the specific problems of mobility and radio access impacts
on the provision of end-to-end QoS.
- What requirements on external networks might be needed to enable QoS
mechanisms within the access network to operate.
- How to adapt QoS concepts for the fixed Internet to the mobile wireless
environment.
Security
Problems are:
Within one access network
• Security interaction with mobility and QoS?
• What requirements on external networks might be needed to enable security
mechanisms within the access network to operate.
Between Networks
• Networks have different identity management systems and security
requirements including confidentiality, integrity and authentication. An E2E
security framework is required.
• Users are required to sign in, multiple times with different operators/accounts.
A single-sign-on is required
Combined mechanisms?
• Mobility, QoS and Security mechanisms have traditionally been designed, each in isolation using different approaches
• When put together in one network, the overall performance has not been as expected.
• To minimise the negative interactions among these mechanisms, they should be designed simultaneously using the same approach and with a common signalling protocol.
Mo
bili
ty M
an
ag
em
en
tQuality
of S
ervice
Security
Challenges
• Within an access network, different design approaches have been
considered for QoS, mobility and security mechanisms
in isolation without considering their inherent interactions
• Access Networks are expected to use different QoS, mobility and security
mechanisms. To achieve end-to-end networking across them is a
challenging task.
Mobile VCE Ubiquitous Services Project
How?
• This will be done by selectively placing a number of enhanced nodes within
the network, capable of communicating with each other.
• New mechanisms will be provided to counteract the negative interactions
between QoS , mobility and security.
Mobile VCE Ubiquitous Services Project
Future Internet
Access Network 1 Access Network 2
Intra access network
signaling
Inter access network
signalingEnhanced nodes
Network layer
Link Layer
Mobility QoS Security
RR
M
Architecture for Enhanced Nodes
S
I
G
N
A
L
L
I
N
G
Mobility Management
Quality of Service
Security
Interactions
between
different
ModulesCommon
signalling
where
possible
Taking optimal decisions in a combined mannerMinimising delays and signalling overhead
Mobility,
QoS and
RRM
Modules
Architecture Components
Initial study
• Major Micro Mobility solutions such as Hierarchical Mobile IPv6 propose having
Mobility Agent(s) within access networks to minimise handover signalling
• Having a node through which all packets flow through will have an effect on the
resources of the network. (i.e. increase congestion which will reduce the network
throughput and the number of users the network can support)
• No work has been done to study how the presence of MAPs affect the resources
within an access network.
Introduction to the problem
Internet
Mobile Anchor
Point (MAP)
Generalised View
NEXT GENERATION INTERNET
Laptop
Different mobility patterns creating different traffic demands and flows
High congestion
Network Throughput with 18 nodes
Network Throughput with 35 nodes
More challenges
• Even within a radio access network, supporting network edge-to-terminal
QoS and Security are challenging.
• QoS and security mechanisms used in the air interface and the wired part
of access networks are different.
• To support end-to-end QoS and security, the parameters of the network
QoS and security should be mapped properly to the parameters of QoS
and security mechanisms used in the MAC layer of the BS (air interface).
End-to-End QoS and Security
End-to End QoS Support in an Interworking Environment
An Example
DiffServ-aware priority Queuing for IP QoS Support
On HSDPA
IP QoS for evolved UMTS
• IP for evolved UMTS CN/RAN.– Low infrastructure cost.
– Mitigated network administration and maintenance.
– End-to-end QoS routing.
• DiffServ for IP QoS– Packets are classified and marked to receive a particular per-hop forwarding
behaviour on nodes along their path.
– Sophisticated classification, marking, policing, and shaping operations need
only be implemented at network boundaries or hosts.
DiffServborder
Data flow
IP QoS for evolved UMTS
SGSN
IP-Based RAN
HLR
GGSNRNCBS
IP-Based CN
HSDPA
HSUPA
• All Previously reported scheduling algorithms for HSDPA consider only one queue per user.
• The scheduling is handled in the MAC layer of the Node B.
• The MAC header has 3 bits dedicated to indicate the queue ID. Thus, each user can have up to 8 simultaneous queues in parallel.
• Each queue may be assigned a priority level. Each DSCP is mapped onto the corresponding priority level. The packets with the same DSCP are forwarded to the correct queue.
Priority Queuing
Priority queuing (Node B architecture)
Pa
cke
t d
istr
ibu
tor
HARQsignaling
CQI
HARQretransmissions
HARQ #1
HARQ #2
HARQ #6
...
Tx ant.
Queue #1
Queue #2
Queue #8
...
Scheduler(MCS & MUX)
Priorityqueues
Queues of the same priority level are
treated equally.
# users
Priority queuing (UE architecture)
Re
ord
eri
ng
qu
eu
e
dis
trib
uto
r
HARQ #1
HARQ #2
HARQ #6
... M
UX
Recovered
data
ACK / NACKCQI
SIRestimator
Feedback
MUX
Rx ant.
HARQsoft combining
Reorderingqueues
Queue #1
Queue #2
Queue #8
...
Killer Applications and Services?
Services and RevenuesR
ev
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ue
pe
r U
se
r (
Re
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nu
e p
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Us
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( ££))
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0.100.10
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0.300.30
0.400.40
0.500.50
0.600.60
0.700.70
0.800.80
0.900.90
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Throughput/Performance Requirement (Kbps)Throughput/Performance Requirement (Kbps)
On-line gaming
Game downloads
Video/TV streaming
MMS
Text Messages
Music
Web browsing
Video phone
Paid applications
Paid services
Source: BT Technology Journal
Trends in media creation/consumption
Source: COMSCOR, JUNIPER RESREACH
Thank You
Any Question?