Transcript Solution proposal for self-organising network use case: Load/Time

An automatic Procedure for Neighbor Cell List
Definition in Cellular Networks
Flavio Parodi, Juan Li, Jose Pradas – Helsinki University of Technology
Mikko Kylväjä, Gordon Alford – Nokia Siemens Networks
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Outline
• Introduction
• Challenges of future wireless networks
• Introduction of self-management
• Neighbor Cell List (NCL) management: the impact of self-configuration
• Proposed algorithm for NCL configuration
• Overview
• Coverage area approximation
• Class 1 algorithms
• Class 2 algorithms
• Class 3 algorithms
• Network adaptation to the new cells
• Centralized approach
• Distributed approach
• Conclusions
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Introduction
• In future years, network operators will have to face an increasing number of
technological challenges:
• The simultaneous operation of different technologies (GSM, (E)GPRS, WCDMA, Next
Generation Mobile Network)
• The need to provide a widespread coverage with high bandwidth requirements (i.e.
Home base stations)
• A tremendous increase in the number of operated network nodes
• A diversified range of services, potentially requiring seamless connectivity
• Furthermore, developed countries will be characterized by an almost saturated
market, with strong competition among operators forcing a reduction in tariffs
• In such a context, management systems are a potential bottleneck for a
successful network operation
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Introduction
• The reduction of operating expenditures (OPEX) and management complexity
are vital for network operators in the years to come
• More efficient and autonomous management systems are crucial to achieve such
targets
• The application of autonomic self-management functionalities would allow for
• A reduced need for human control and intervention
• The capability of adaptation in presence of new nodes (self-configuration)
• The possibility of increasing performances, by optimizing network parameters (selfoptimization)
• A more efficient and well-timed report, diagnosing and fixing of malfunctions (selftesting and self-healing)
• At present, 3GPP LTE standards define the support for the the self-configuration
and self-optimization functionalities [1]:
• The self-configuration takes place in the pre-operational state
• The self-optimization takes place during the operational state
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
NCL self-configuration
• An automatic NCL self-configuration feature would allow for
• A reduction of site visits related costs
• An easier and more reliable hardware installation
• The proposed algorithm can be subdivided in two different parts
• The first one aims at configuring the NCLs of a newly deployed BS
• The input of such part is the planned NCL or, if the latter is not available, a pool of network
information
• Once such part of the algorithm has been performed, all the cells connected to the new BS
have their own NCLs
• The second part performs the adaptation of the neighboring cells to the new node
• The information contained in the NCLs is used to notify the neighbors of the presence of
the new BS
• At the end of the algorithm, the NCLs in the neighboring cells are up-to-date, i.e. they
include the cells controlled by the new BS
• The algorithm is executed by a self-configuration manager, to be potentially
implemented in either a centralized or a distributed fashion
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Proposed algorithm: NCL configuration
• The NCL configuration is carried out separately for each one of the new cells
• The implementation reflects two alternative scenario
• The NCLs were planned before the deployment
• This is likely to happen for the installation of multiple BSs
• We assume the NCLs are stored in a network database, each of them associated with the
respective cell by means of an identifier
• The NCLs are not available
• The self-configuration functionality calculates the NCLs on-line (i.e. during the selfconfiguration process)
• This approach may be appropriate when deploying a single/few BSs
• We assume a network database contains various network information: BSs’ coordinates,
antenna parameters (main lobe direction, beam width, radiation pattern), radiated power
values
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
NCL configuration: flowchart
1. Query database: is the NCL available?
yes
no
2. Get a list of all N neighbors i, i=1,…,N within a
range R from the new cell
3. Approximate coverage areas of the new cell and
of a generic cell i in the retrieved list
4. Detect overlap: is there overlap between new cell and
cell i coverage areas?
no
yes
Add cell i to the NCL
i=N?
no
yes
Store NCL; end
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
i=i+1
NCL configuration: coverage area approximation
• In case the NCL is calculated during the self-configuration process, the coverage
areas of all potential neighbors are considered
• Two cells are identified as neighbors if their coverage areas overlap
• Depending on the available amount of information, the coverage areas can be
approximated in different ways, each corresponding to a specific class of
algorithms:
• Class 1  only geographical information available (cell coordinates)
• Class 2  coordinates and antenna parameters available
• Class 3  coordinates, antenna parameters and power values available
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Coverage Area Approximation: class 1 algorithm
• Neighbors are determined based only on distance
• Coverage areas cannot be determined due to the lack of coverage information
• All potential neighbors are included in the NCL
• The range value R is critical:
• If R is too small, some neighbors could be missed
• If R is too big, some cells could be included in the NCL even if they are not neighbors
of the new one
e1
Cells
e2
d1
d2
d3
a2, a3, b1, b2, b3, c1, c2, c3, d1,
d2, d3, e1, e2, e3
e3
are included in cell a1 Neighbor
Cell List
a1
R
a2
a3
c1
b1
b2
b3
c2
c3
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Coverage Area Approximation: class 2 algorithms
• Cell coordinates and antenna parameters are used to approximate coverage areas
• Depending on the available antenna parameters, different ways of approximation can be
considered:
• Class 2a: only main lobe direction  circle approximation
• Class 2b: main lobe direction, beam width  sector approximation
• Class 2c: main lobe direction, radiation pattern  pattern approximation
• Since no information on radiated power is available, the maximum coverage range r is
required as an input to the algorithm
• The same value of the diameter is used to approximate all coverage areas
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Coverage Area Approximation: class 2 algorithms
•
The detection of overlap is carried out by checking if the coverage area
perimeters of two cells intersect
•
Circle approximation: the perimeters intersect
if the sum of the radiuses is less than the
distance between the centers
Approx.
coverage
area
r
r d
O
Approx.
coverage
area
a 1Oi
Oi
Oa1
r/2
r/2
a1
a2
•
Sector approximation: the following intersections
are checked: between sector sides, between
sector side and circumference arc, between
circumference arcs
a3
P
Oa1
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
A
B
Oi
i
Coverage Area Approximation: class 2 algorithms
•
Pattern approximation: the perimeter of a potential
Pa1k
neighbor is approximated through a series of
segments. For the new cell, the segment linking
Pij
the center and a perimeter point is considered;
if it intersects one of the perimeter segment of
•
Pij+1
i-th cell’s
the potential neighbor, the coverage
areas overlap.
Ik
New cell’s
coverage
area border
Oa1
coverage
area border
The lack of knowledge about the radiated power values does not allow to fix the
value of r, which has to be set based on heuristic rules
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Coverage Area Approximation: class 3 algorithms
•
•
•
•
•
The availability of the radiated power value allows to fix the maximum coverage
range r, i.e. the size of the coverage areas
On the coverage area border, the following equation holds:
Ptx  G  AF ( )  LP  S MT
where Ptx indicates the radiated power, G the antenna gain, AF the antenna
factor, LP the path loss, SMT the sensitivity of the mobile terminal
Fixing the mobile terminal sensitivity, the path loss value at the perimeter of the
coverage area can be calculated
The Okumura-Hata formula is used to model the link loss
Once the path loss value is known, the maximum range is calculated solving
the O-H formula with respect to r [2]:
LP  46.3  33.9 log 10 f 13.82 log 10 hb 1.22  (44.9  6.55 log 10 hb ) log 10 r
•
As far as the coverage area shape is concerned, the same methods of
approximation as algorithms 2 are used (and, therefore, the same rules for
overlap detection apply)
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
NCL configuration: issues
•
The NCL configuration algorithm provides the NCL for a new cell
•
•
•
In the autonomic framework defined in [3], the presented algorithm is used to
determine the neighbors of a cell once it joins the network
The calculated NCL may include cells which are not actual neighbors
•
The best NCL is the one made up by only the actual neighbors of the new cell
•
The goal of the NCL definition algorithms is not to find the best NCL, as the following
optimization phase should take care of dropping the neighbors with low HO share
•
If the initial NCL includes all the actual neighbors, the best NCL can be found simply
by pruning the unused NCL entries [3]
The required computational load depends on the type of approximation for the
coverage area
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Algorithms for the network adaptation to the new cells
• After the NCL is defined and stored in the new node, the network should react to
its presence
• The neighbors of the new BS should add the new cells in their NCLs
• The network database should also be updated with the new adjacencies, in order
to keep the information aligned with the actual status of the network
• The following slides present an implementation for the NCL definition and
network adjustment procedure in LTE networks
• We assume the network nodes are linked through an IP network
• Two possible approaches:
• Centralized: the self-configuration functionality is exploited by a specific network
element
• Distributed: the self-configuration functionality is exploited by a module within each
eNB
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Network adaptation: centralized solution
Network
Database
Self-configuration
element
New eNodeB
1
2
Database query
3
Database answer
Neighboring eNodeB
NCL request
NCL Definition
algorithm
4
NCL response
5
6
7
New adjacency notification
ACK/NACK
Adjacency update
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
8 Authentication
Centralized solution: overview
• The new node must be able to address the self-configuration element
• Pros:
• The intelligence is located in a single, defined element
• Cons:
• Potential increase in the signalling to the centralized node
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Network adaptation: distributed solution
Network Database
New eNodeB
Self-configuration
module
1
Neighboring eNodeB
IGMP
module
Self-configuration
module
IGMP
module
Database query
2
Database answer
NCL Definition
algorithm
3 Authentication
4
Send multicast data
ACK/NACK
7
8
IGMP
Membership_report
Adjacency update
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
6
5
IGMP
Membership_report
Distributed solution: overview
• The proposed solution allows a multicast group to be created, including all the
neighbors of the new node
• Efficient communication support for self-optimization
• To support multicast, the following protocols should be supported
• IGMP (Internet Group Management Protocol)
• Multicast routing protocol, e.g. DVMRP (Distance Vector Multicast Routing Protocol ),
PIM (Protocol-Independent Multicast )
• Reliable multicast protocol
• Pros:
• Reduced need for signalling to network management layers
• Cons:
• An intelligence is needed in the nodes
• Looser control on the self-configuration process
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
Conclusions
• A procedure for automatically defining the NCL and updating the adjacencies
accordingly in the network was defined
• The procedure is carried out by a self-configuration functionality
• The considered procedure allows for a flexible approach to self-configuration
• The NCL can be retrieved from a database or calculated online, depending on the
amount of available planning data
• The implementation can follow either a centralized or a distributed approach
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007
References
[1] 3GPP TS 36.300 v8.0.0, Evolved Universal Terrestrial Radio Access (E-UTRA) and
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description;
Stage 2
[2] J. Laiho, A. Wacker, T. Novosad, editors. Radio Network Planning and Optimisation for
UMTS, 1st ed., John Wiley & Sons, 2002.
[3] D. Soldani, G. Alford, F. Parodi, M. Kylväjä. An Autonomic Framework for Self-optimizing
Next Generation Mobile Netwoks. IEEE, WoWMoM IWAS, Helsinki, Finland, June 2007.
[4] R.Guerzoni, I. Ore, K.Valkealahti, D.Soldani. Automatic Neighbor Cell List Optimization
for UTRA FDD Networks: Theoretical approach and Experimental Validation,
IWS/WPMC, Aalborg, Denmark, 2005
[5] 3GPP TR 25.912 v7.0.0, Feasibility study for evolved Universal Terrestrial Radio Access
(UTRA) and Universal Terrestrial Radio Access Network (UTRAN)
[6] 3GPP TR 25.814 v7.0.0, Physical layer aspects for evolved Universal Terrestrial Radio
Access (UTRA)
[7] 3GPP TR 23.822 v1.2.3, 3GPP System Architecture Evolution: Report on Technical
Options and conclusions
1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June,
2007