Ericsson AB
11 Nov -09 by Åke Davidsson
Introduction to a product it’s challenges and solutions GSM Femto Cell Solution
Background - Operator value
An Operator Enabler to win the ”fight for the home” –3-play Telephony Data (mobile, PC) TV
Background - Ericsson Ericsson decided to get into the home premises. By combining mobile telephony, IP and WLAN Reducing the size of a mobile cell down to ”home” coverage Using IP as transport
Ericsson Internal 2 2009-11-09 Background End-User Value
Maximum Convenience One phone, at home and on the move Over 2 billion No need to replace current GSM or GSM/WCDMA phone deployed phones
Save money Replaces fixed phone and subscription Low tariff at home
Easy to get going Easy to use installation (plug & play) Uses any existing IP backhaul
Ericsson Internal 3 2009-11-09
GSM Femto Cell Solution Network, Step 1 - Before Femto
GSM RF HLR
MACRO
BSC MSC
SGSN Gateway
Internet Internet OSS
802.11b/g Broad band Access
Ethernet Mobile system - GSM
Ericsson Internal 4 2009-11-09 GSM Femto Cell Solution Network, Step 2 - With Femto
GSM RF Radius - AAA HLR
MACRO
BSC MSC
GSM RF SGSN FEMTO Gateway Femto BSC Internet Internet OSS
802.11b/g Broad band SEGW Access
Ethernet ACS File server
Mobile system - GSM
Ericsson Internal 5 2009-11-09
Modems/home routers connecting to broadband - automatic To achieve the best possible Quality of Service (QoS) for GSM it is recommended to replace existing ADSL modems/home routers with the Femto Cell CPE.
Before: The Dynamic Host Configuration Protocol (DHCP) is a networking protocol used by devices (DHCP clients).
DHCP DHCP client server
Ethernet/DSL IP Bridge IP Ethernet Ethernet or ADSL CAT5 FHY
After: DHCP DHCP DHCP DHCP client server client server NAT
Router IP IP Ethernet Ethernet or ADSL CAT5 FHY
Internet connectivity by auto configuration in these cases if Internet Service Provider give out WAN IP address.
Ericsson Internal 6 2009-11-09 Discovery - How will the Femto Cell Customer Premises Equipment (CPE) discover the Base Station Controller (BSC) without end-user configuration?
- CPE = Customer Premises Equipment = the home equipment
Femto Secure tunnel establishment Cell CPE SEGW Femto Cell SIM GW SG5500 R1 BSC R1 BSC FQDN Internet SEGW FQDN RBS Fp
DNS Query DNS eDNS IPWorks 4.2 NTP
A fully qualified domain name (FQDN), referred to an absolute domain name is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS).
Ericsson Internal 7 2009-11-09
How will the Mobile find the Femto Cell? PLMN = public land mobile network Home = H Visitor = V Macro cell and a small Femto cell
PLMNA
PLMNB
’Normal’ MS SIM: HPLMN = PLMNA VPLMN Prio List: Femto user MS SIM: - HPLMN = PLMNB VPLMN Prio List: PLMNA 2 PLMN method All MS with Femto SIM can use all Femto Cells
Ericsson Internal 8 2009-11-09 User Notification
In Macro Network- as usual At Home
H O om pe O e rato pe r rat
Network info sent from MSC No info sent from MSC (Mobile exchange) The Mobile uses information stored on SIM ”Operator Name”
Ericsson Internal 9 2009-11-09
No handovers to other cells
Macro network is not aware of the Femto cells => no handovers into a femto cell
The Femto network is not aware of which macro cell that is close to a specific femto cell => no handovers out of a Femto cell
Ericsson Internal 10 2009-11-09 Search for Synch
The Radio Base Station (RBS) part of the CPE starts scanning the 900 and 1800 MHz bands for BCCH carriers
The strongest one found, independent of operator, is used as frequency reference
The broadcast control channel (BCCH) in the GSM cellular standard. The BCCH carries a repeating pattern of system information messages that describe the identity, configuration and available features of the BTS.
Ericsson Internal 11 2009-11-09
QoS in Femto solution
Quality of Service, a measure of the reliability of a computer network or telephone service
In the Femto solution QoS is defined as low delay and low packet loss for GSM speech and GPRS traffic.
”... for speech a late packet is a lost packet...”
Ericsson Internal 12 2009-11-09 Delay is created by queues
Every node has a queue for outgoing packets If more incoming packets arrive than the outgoing interface can send, congestion will occur.
Radius Dslam 1-st router Router HLR
SGW MSC Internet Internet SGSN Router FW BSC
Femto
OSS ACS
A Digital Subscriber Line Access Multiplexer Dslam allows PC telephone lines to make faster connections to the Internet.
Ericsson Internal 13 2009-11-09
Congestion
Fast Congestion is created when a fast Dslam 1-st router link is connected to a slower connection.
Slow It is assumed that biggest difference in speed occurs between the home and the dslam/1st-router. 3-pla y un it It is most likely that congestions will
Fast appear in these two queues (but it can appear in other nodes due to load).
Fast
Ericsson Internal 14 2009-11-09 QoS mechanisms
Two techniques exists 1. Reserve bandwidth Use DiffServ, CoS, multiple ATM PVC´s. Requires that sending and receiving nodes are configured to match each other. 2. Traffic shaping Make sure you are the weakest link in both directions. This way the congestion will always appear in your own node, and shaping rules can be defined to priorities the important traffic.
At Femto, no control over access network was agreed (i.e. no access network control) and hence traffic shaping was the only option.
Femto CPE is prepared for the reserve techniques above. Using reserve techniques doesn't reduce user data traffic more than the number of bit/s that is specified.
Ericsson Internal 15 2009-11-09
Traffic shaping
Upstream and downstream are handled separately and have a bit different characteristics.
The shaping required to get good QoS for GSM is linear to the bandwidth available. The shaping in percentage of bandwidth is the same for a fast connection as for a slow one.
Ericsson Internal 16 2009-11-09 Traffic shaping - upstream
GSM reserves a piece of the total bandwidth and the rest is for LAN traffic. HTB Rate:90% An advanced technique is used where the GSM can lend bandwidth to LAN traffic and vice versa (i.e. ceil). LAN traffic is separated to give priority for ACK and ICMP packets. This speeds up downlink since the ACKs return faster for the TCP streams. The end-user will experience HTB HTB faster access to websites, for example, during competing GSM Data Rate:130 Kbit/s Rate: 90% - GSM traffic. Ceil:90% Ceil:60% || 90% When throttling is used TCP sessions will backoff to use up less bandwidth. Normally this also affects UDP streams since congestions should be handled at application layer and for example reduce speed or change codec. fifo HTB HTB The shaping throttles LAN traffic down to 60 % of Prio 1 Prio 2 TCP ACK prio Other data available bandwidth during an ongoing call. ICMP prio When there is no ongoing calls, the throttling is set to 10% GSM of available bandwidth (to prevent too large queues to be built up).
HTB = Hierarchical token bucket SFQ SFQ FIFO = First In First Out SFQ = Stochastic Fair Queuing TCP = Transmission Control Protocol ICMP = Internet Control Message Protocol LAN/WLAN
Ericsson Internal 17 2009-11-09
Traffic shaping - downstream
The outgoing interface (LAN) is of course faster than the incoming but we need to make sure the outgoing dslam/1st-router queue is kept small, hence shaping is HTB required in Femto CPE and hence incoming packets Rate:90% are throttled down. Same problems with assymetric burst traffic like in upstream shaping. This is due to to burst traffic, normally created by TCP sessions (i.e a small amount HTB Data of ACKs upstream generate lots of downstream traffic Rate:40% || 90%-GSM and vice versa). Ceil:90% The shaping is performed at LAN interfaces and hence no shaping rules for GSM is needed (already terminated). The shaping throttles LAN traffic down to 40 % of SFQ available bandwidth during an ongoing call. When there is no ongoing calls, the throttling is set to 10% of total bandwidth (to prevent too large queues to LAN/WLAN be built up).
Ericsson Internal 18 2009-11-09 Bandwidth estimations
In order to have an effective shaping we need to know how much bandwidth we have. Femto CPE uses an advanced technique to find a router as close to the DSLAM/1st-router as possible and then performs a small packet burst. Femto CPE checks how far apart the incoming packets comes back in the burst. The weakest link will create the biggest gap between packets. In the DSL case the trained speed is used instead to get asymmetrical values (UL/DL).
Ericsson Internal 19 2009-11-09
What happened
Close down of project due to lack of a solid business case
Ericsson Internal 20 2009-11-09 Ericsson Internal 21 2009-11-09