Soft & Softer Handover In UMTS System
Handovers are an important part of every cellular communication system. They are used for providing mobility in cellular architectures. In UMTS systems different handover types have been introduced to cope also with other requirements as load control, coverage provisioning and offering quality of services. Handover aims to provide continuity of mobile services to a user traveling over cell boundaries in a cellular infrastructure. For a user having an ongoing communication and crossing the cell edge, it is more favorable to use the radio resources in the new cell – also called the target cell because the signal strength perceived in the “old” cell worsens as the user penetrates the target cell. The whole process of tearing down the existing connection in the current cell and establishing a new connection in the appropriate cell is called “handover”. The ability of a cellular network to perform efficient handovers is crucial to offer [...]
Categories: UMTS Tags:
RRC Measurements Cheat Sheet (FDD)
RRC Measurements Cheat Sheet (FDD) is a one page help guide. Cheat sheets are useful when debugging an issue or testing a test cases and you just need a quick look instead of going into the specification. In this document we have recorded all the RRC measurements and the meaning of those events. Please let us know what you think about this. If you have similar help sheet/cheat sheet which you have created and you want to share please send to us (contact@3glteinfo.com). We will publish those through 3glteinfo. Download Here
RLC Bitmap Super Field (BITMAP-SUFI)
The BITMAP SUFI consists of the following fields: Type identifier field(BITMAP) LENGTH Filed First Sequence Number(FSN) Bitmap The BITMAP SUFI fields in the STATUS PDU are as follows: Type = BITMAP LENGTH FSN Bitmap LENGTH The LENGTH is a 4 bits long field. The LENGTH field signifies the size of bitmap in octets. The size of bitmap in octets = LENGTH + 1 So if, LENGTH = 0000 = 0 Size of bitmap = 0 + 1 = 1 octet FSN FSN is the sequence number of the first bit in the bitmap. FSN is 12 bits long. Bitmap In bitmap each bit position signifies whether FSN + bit_position is correctly received or not. bit_position can have two different values: 1 Sequence Number = (FSN + bit_position) has been correctly received. 0 Sequence Number = (FSN + bit_position) has not been correctly received. Example Suppose the receiver needs to send [...]
Categories: RLC Tags:
MAC-ehs PDU Structure with Example
There are two different types of MAC HSDPA PDU format depending upon the upper layer configuration. MAC-hs MAC-ehs In this tutorial only MAC-ehs is covered. In this case the MAC HSDPA PDU is consists of MAC-ehs header One or more reordering PDUs Each reordering PDU consists of one or more reordering SDU belonging to the same priority queue. Header Elements LCH-ID (Logical Channel Identifier): 4 bits The LCH-ID field provides identification of the logical channel at the receiver and the re-ordering buffer destination of a reordering SDU. LCH-ID Designation 0000 Logical Channel 1 0001 Logical Channel 2 . . . . . . . . . . . . . . . . . . . . . . . 1110 Logical Channel 15 1111 Logical Channel 16 TSN (Transmission Sequence Number): 6 bits The TSN field provides an identifier for the transmission sequence number on the HS-DSCH. The TSN [...]
MAC HSDPA PDU (MAC-hs)
There are two different types of MAC HSDPA PDU format depending upon the upper layer configuration. MAC-hs MAC-ehs In this tutorial only MAC-hs is covered. MAC-hs In this case the MAC HSDPA PDU is consists of MAC-hs header One or more MAC-hs SDU NOTE: A maximum of one HSDPA PDU is transmitted in on TTI Header Elements VF (Version Flag): 1 bit VF field is there to provide extension capabilities. This should be set to zero for now Queue ID (Queue Identifier): 3 bits The Queue ID field provides identification of the reordering queue in the receiver. TSN (Transmission Sequence Number): 6 bits or 9 bits The TSN field provides an identifier for the transmission sequence number on the HS-DSCH. The TSN field is used for reordering purposes to support in-sequence delivery to higher layers. NOTE: Only for TDD 1.28 Mcps configuration TSN can have a value of 6 bits [...]
3GPP Message Decoder
3GPP message decoder is a very simple but powerful tool to decode GSM, UMTS, LTE, IP messages. This is developed by http://www.protocolanalyze.com. 3GPP decoder is a simple application using Wireshark to decode messages. 3GPP Message Decoder has a very simple interface. The user interface has the following sections: Enter the HEX message to decode in the top text area. You can choose between GSM, WCDMA, LTE or IP Protocol. Use the dropdown to select between different message types to select. The decode button. Decoded message window Message Type Supported 3GPP Message Decoder supports the following message types. GSM GAN TCP GAN UDP GSM CCCH GSM SACCH LLC NAS SNDCP SNDCPXID UMTS NAS RRC BCCH.BCH RRC BCCH.FACH RRC DL.CCCH RRC DL.DCCH RRC DL.SHCCH RRC MCCH RRC MSCH RRC PCCH RRC UL.CCCH RRC UL.DCCH RRC UL.SHCCH RRC SIs (SIBs and MIB) LTE RRC BCCH.BCH RRC BCCH.DL.SCH RRC DL.CCCH RRC DL.DCCH RRC PCCH [...]
Basics of data transmission in a UMTS system
In a UMTS system, the maximum supported downlink data rate is 2.048 Mbps. With other technologies such as HSPA, LTE, higher data rates are possible, but we look at data rates for UMTS only systems. Each application has a certain Quality of service (QOS) requirement. A user who wishes to run a application that demands high data rate informs the network of his throughput requirement in Quality Of Service (QOS) attributes during PDP context activation. It is from this message that the network becomes aware of the user’s data rate requirement. Apart from data rate, other parameters like application’s error resilience, time sensitivity etc is negotiated. If the network could fulfill the requirement, it informs the user by accepting and activating the PDP context and sets up a Radio Access Bearer (RAB). Network provides channel details that UE has to use in order to send and receive data in a [...]
Categories: MAC Tags:
