La mercantilización de la información: la nueva era
B) Aspectos formales de las noticias
6. Resultados del análisis
Just as we defined an architecture for Quality of Service (QoS) end-to-end UMTS, with the appearance of evolved packet system (EPS) is also necessary to define a set of parameters and mechanisms in order to ensure quality of service in this new system. Recalling that EPS is the set of SAE with LTE, EPS has significant
improvements in the quality of service in relation to 3GPP systems that precede it.
7.3.1 EPS architecture and quality of service
For EPS architecture is clearly defined with attributes and functions to achieve a quality point to point service.
Figure 88 - Architecture EPS QoS bearer channels
Service quality point to point means you must have a service carrier and EPS external carrier, the latter in order to support services and from outside the network nodes. The EPS bearer service is a service carrier and a carrier radio access.
7.3.2 EPS Carrier
Considering the qualities of an "All IP" and the nature of bursts in data services, from 3GPP Release 8 introduces the concept of EPS carrier, called from now on as
"carrier" for simplicity.
The carrier is a concept from which identifies packet flows receive the same
treatment in terms of quality of service between the terminal equipment (UE) and the gateway PDN-GW. PDP context is equivalent to the standards used in 2G/GPRS and 3G/UMTS. The carrier is composed of three elements, namely:
• S5 Carrier: implemented through a tunnel that transports packets between the S-GW and the PDN-GW
• S1 Carrier: implemented through a tunnel that transports packets between the S-GW and eNodeB
• Radio carrier, implemented by a protocol connection with RLC (Radio Link Control) between eNodeB and the EU.
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The elementary stream data in EPS is known as SDF (Service Data Flow).This flow is characterized by five aspects: source IP, destination IP address, source port, destination port and protocol for identifying the protocol is over IP. This serves to determine points where the flow begins and ends, and to determine which application or service is in use.
In the terminal there is a carrier for each class of service quality and IP address, which means that a terminal can have both multiple IP addresses assigned using different services and therefore have different carriers associated with multiple qualities of service. The carrier is the differentiating factor that facilitates traffic allocation quality of service requirements.
You can define two types of carriers as a key differentiating factor: the carriers with a guaranteed bit rate (GBR, Guaranteed Bit Rate) and those that do not guarantee (non GBR, non Guaranteed Bit Rate). Then one can assume that a service using a carrier GBR no packet loss due to congestion, which is carried out by the different admission control functions located in different network nodes. With the other type of carrier cannot be assured the above. A GBR carrier to carry out its function properly you need to reserve network resources, so that its place is not for long periods, while a non-GBR bearer does not reserve resources so if your facility allows for longer periods time.
Similar to the classification of carriers GBR and no mention is made of dedicated carriers or default. The default carrier is set when the terminal is connected to the network and is maintained by the terminal while maintaining the same IP address.
Because the carrier is maintained for long periods then classified as non-GBR. To provide different qualities of service to different packet flows requires the use of dedicated carrier, which can be GBR or not RBM. The mapping of packet flows is dedicated to carrying through policies in the network that can be modified by the network operator.
7.3.3 QoS parameters
EPS carrier is characterized by the following parameters:
• Allocation and retention priority (ARP Assignation Retention Priority): refers to priority mechanisms used for allocation and retention. This parameter is used for example in cases where there is congestion and must decide which carriers are preserved and which discarded.
• Guaranteed bit rate (GBR, Guaranteed Bit Rate): This parameter applies only to carriers GBR requiring guaranteed quality of service and voice service.
• Maximum bit rate (MBR, Maximum Bit Rate): this parameter is set a limit for bit rates of services offered.
• Class Identifier quality of service (QCI, Quality of Service Class Identifier) is used within the access network as a reference to a number of parameters that control the processing of packets through different network nodes. Each QCI is associated with a number of characteristics
QCI Resource Type Priority PDB (ms)1 PLR2 Examples of services
13
GBR
2 100 10-2 Conversational voice
23 4 1000 10-3 Conversational video
33 3 50 10-3 Real-time Gaming
43 5 300 10.6 Video not conversational
53
No GBR
1 100 10.6 IMS Signaling
64 6 300 10.6 Video streaming, www, email, chat, ftp, p2p, etc.
73 7 100 10-3 Voice, video, interactive game
85 8 300 10.6 Video streaming, www, email, chat, ftp, p2p, etc.
96 9 300 10.6 Video streaming, www, email, chat, ftp, p2p, etc.
1must be subtracted from a delay of 20 ms between the base station and PCEF to determinate the PDB that applies to the radio interface. This is an average of delay considering the cases in which the PCEF is close (approximately 10 ms) and which is far (about 50 ms). It should be noted that the PDB set an upper limit, so you should expect that delays are significantly lower, especially for GBR traffic.
2Applies to the radio interface between the UE and the eNodeB.
3associated with operator-controlled services.
4can be used for prioritizing specific services according to the specification of the operator.
5can be used to carry dedicated user or premium user groups with privileges.
6carriers typically used for default unprivileged users.
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• Resource type: determines whether the carrier is GBR or not RBM.
• Priority: is used to differentiate the connections SDF. Each QCI is associated with a priority, with 1 being the highest priority.
• Packet delay budget (PDB, Packet Delay Budget): refers to the possible latency of data packets transported between the terminal and the PDN-GW.
This is the same for the downlink and up to one QCI.
• Packet loss rate (PLR Packet Loss Ratio): describes the maximum rate of packets transmitted to the upper layer of all packets processed by the link layer. Like the PDB is the same for the uplink and downlink for the same QCI.
• In addition to the carrier level parameters, there is a parameter of quality of service associated with the terminal called maximum aggregate bit rate (AMBR, Aggregate Maximum Bit Rate) which applies only to non-GBR bearers. Serves to limit the bit rate of subscribers differently, it is also defined but not for a carrier to a carrier group of a subscriber
7.3.4 Packet Filters
A packet filter has to be created in the PDN-GW (and signaled the EU) of each SDF in order to allow proper allocation of the data in the EPS bearer channel and correct routing. The EPS bearer channel is associated with a TFT (one on one in the UL and DL) and therefore an EPS bearer channel can carry only one SDF, while all data from the same EPS bearer experience the same QoS. The SDF can be assigned a same carrier EPS only if they have the same QCI and ARP.
The packet filters are sequentially applied to the input data (in the EU in UL and DL in the PDN GW) according to values of packet filters in the Index-Evaluation-Priority. If the data do not match should be sent to the carrier that has no associated packet filters. If no such carrier data must be returned.
The packet filter package has a unique identifier (1-8) in the TFT and consists of one or more of the following attributes in terms of its configuration with respect to the application that entail:
• Source / Destination IP address subnet mask
• Number of protocol overhead (eg, TCP / UDP)
• Destination port range.
• Source port range.
• Index IPSec security parameter.
• Service type, identifies the quality of service
• Flow level, only used for IPv6
7.3.5 Mapping the QoS parameters for UMTS and EPS
Since its beginning in LTE / SAE will have to live with 2G/GPRS and 3G/UMTS networks, it is necessary to map the parameters between networks as they are distinct together. The following figure summarizes the mapping between parameters.
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PDP R97/98 PDP R99 EPS R8
Delay Traffic Class Carrier Type
Priority traffic management
Reliability SDU Error Rate PLR
Bit error rate residual Delivery of erroneous SDU
Peak transfer rate Maximum bit rate for uplink MBR
Maximum bit rate for downlink
Precedence ARP ARP
Average transfer rate N/A N/A
N/A Maximum SDU size N/A
N/A Transfer delay PDB
N/A GBR GBR
N/A N/A AMBR
Figure 91 - Mapping of QoS parameters for UMTS and EPS