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Blog 2018-10-16T19:22:55+00:00

Stage 4: Authentication and Security

Stage 4: Authentication and Security Stage 4: Authentication and Security Authentication ensures that the user is authorized to use particular network services. EPS AKA is the authentication and key agreement procedure used for the mutual authentication of the UE and the network. In LTE, encryption is possible for the NAS, RRC and user plane over the radio network. Different encryption algorithm options are provided for each of these protocol layers. Integrity protection is done on the NAS and the RRC signaling messages. Authentication requests and authentication response messages trigger counter pegs. Reason for failures are normally indicated in this cases. After successful completion of the authentication procedure the MME picks the NAS algorithms based on the UE capability [...]

By | March 28th, 2019|4G-LTE Optimization Part-1|0 Comments

Stage 3: Network Attach

Stage 3: Network Attach Stage 3: Network Attach The UE initiates the attach procedure by transmitting an RRC Connection Setup Complete message (to the eNB) containing the Attach Request message intended for the MME. The Attach Request message contains the old GUTI or IMSI, the NAS key set identifier, the UE network capability and an ESM message container (which has the PDN Connectivity Request). The PDN Connectivity Request Message indicates whether the UE wants to perform the IP address allocation during the execution of the procedure and, when known, it indicates the UE’s Ipversion capability (IPv4, IPv4/IPv6, IPv6), which is the capability of the IP stack associated with the UE. This message normally triggers a counter, in most [...]

By | March 28th, 2019|4G-LTE Optimization Part-1|0 Comments

E-UTRA States

E-UTRA States E-UTRA States A UE is in the RRC Connected state when an RRC connection is established, otherwise, the UE is in RRC Idle state. The RRC connection is always initiated by the UE and, typically, the network initiates the release of the RRC connection. The RRC states can further be characterized as follows: RRC Idle: UE-controlled mobility, The UE monitors a paging channel to detect incoming calls and system information changes, The UE performs neighboring cell measurements and cell (re)selection, The UE acquires system information, and A UE-specific DRX may be configured by the upper layers. RRC Connected: Transfer of unicast data to/from the UE, The UE may be configured with a UE-specific DRX at lower [...]

By | March 27th, 2019|4G-LTE Optimization Part-1|0 Comments

RRC Connection Setup

RRC Connection Setup RRC Connection Setup RRC connection establishment involves the establishment of SRB 1. The E-UTRAN completes RRC connection establishment prior to completing the establishment of the S1 connection (i.e., prior to receiving the UE context information from the EPC). Consequently, AS security is not activated during the initial phase of the RRC connection. During this initial phase of the RRC connection, the E-UTRAN may configure the UE to perform measurement reporting. When the UE sends an RRC Connection Request to the eNB, this message is sent using the RLC-TM, and includes the UE identity, and the establishment cause (Emergency, High Priority Access, Mobile-Terminated Access, Mobile-originated Signaling, Mobile-Originated Data). Once the eNB receives this message, this typically [...]

By | March 26th, 2019|4G-LTE Optimization Part-1|0 Comments

Improving RACH Success

Improving RACH Success Improving RACH Success The dynamic range of a UE is defined by its minimum and maximum transmit power. On the other hand, the dynamic range of the random access procedure is defined by the product of the preamble step size (powerStep) and the max number of preambles (TransMax). For example, if powerRampStep = 2 dB, and preambleRetransMax = 10, the preamble dynamic range will be equal to 20 dB. This is far less than the UE’s dynamic range. Therefore, it is imperative the initial preamble transmit power, defined by the open-loop power control equation, is accurate. However, in very good RF conditions, the initial preamble transmit power could be underestimated. This can result in all [...]

By | March 26th, 2019|4G-LTE Optimization Part-1|0 Comments

Timeline for PRACH Probes

Timeline for PRACH Probes  Timeline for PRACH Probes  When the eNB sends a Back-off Indicator (BI) in the RAR sub-header, it is directing the UE to back off the next preamble transmission. Based on this BI value (x milliseconds), the UE will generate a random back-off value, say y, in the range of 0 to x milliseconds. The UE may transmit the next preamble, at the next valid subframe as defined by the eNB PRACH Configuration Index, after t+3+w+y. This back-off process randomizes retransmissions resulting in reduced chances of collision of preambles. To get updated with posts on new technologies like Artificial Intelligence, Machine Learning, 5G-NR, 4G-LTE, 3G-UMTS and 2G-GSM technologies, you can connect with us on Facebook/ LinkedIn.

By | March 25th, 2019|4G-LTE Optimization Part-1|0 Comments

Preamble Transmission Power

Preamble Transmission Power Preamble Transmission Power The random access is often the first transmission from the UE, and it is a short transmission (less than 3ms at most). Consequently, the network does not have an opportunity to power control the PRACH transmitted by the UE. Instead, the UE must estimate the minimum amount of power it needs to send the access request without causing excessive interference. The UE receives a number of key parameters for PRACH power control in SIB 2, including: 1.Preamble Initial Received Target Power: The power level the eNB would like to receive for a random access. The default value is -104 dBm. 2.Power Ramping Step: The amount of additional power to be used every [...]

By | March 25th, 2019|4G-LTE Optimization Part-1|0 Comments

PRACH Power Calculation

PRACH Power Calculation PRACH Power Calculation After receiving the SIB Type 2 information, the UE determines the preamble transmit power. These parameters include the Preamble Initial Target Power that the cell wants to receive the preamble at, the maximum number of preambles the UE may send during the random access procedure, the power increase value in decibels between successive preamble transmissions and the cell Reference Signal transmit power per reference signal resource element. Typically, SIB2 is received at system acquisition time and cell reselection time. When the random access procedure is initiated, the UE executes the following sequence: 1.Measure Reference Signal Strength: The UE measures the averaged Reference Signal Received Power (RSRP) over the defined measurement bandwidth of [...]

By | March 23rd, 2019|4G-LTE Optimization Part-1|0 Comments

Random Access Preamble Generation & Selection

Random Access Preamble Generation & Selection Random Access Preamble Generation & Selection This slide shows how the random access preamble is constructed. The eNB broadcasts root sequence index and cyclic shift, as well as number of non-dedicated preambles in a cell. There are 64 preambles available in a cell. A UE in the cell listens to the broadcast, generates 64 preambles, and randomly picks out one of the number of non-dedicated preambles (preamble 0 ~ # of non-dedicated preambles -1). The root sequence index and the cyclic shift are determined by network planning. The cyclic shift is related to the size of the cell. There are total 838 root sequences available. The length of each root sequence is [...]

By | March 23rd, 2019|4G-LTE Optimization Part-1|0 Comments

Preamble Format Examples

Preamble Format Examples Preamble Format Examples There are four possible formats for the random access preamble, differing by the length of the fields within the preamble. Bigger preambles take longer to transmit, but are better suited for larger cells. The specific format to be used is set in SIB 2. SIB 2 also indicates when, and in which system frames and subframes, the preamble may be sent. The specific preamble sequence to be transmitted is selected randomly using the root index and cyclic shift information from SIB 2. There are a total of 64 different sequences available in each cell. The initial target power level determines how loud the preamble transmission can be to start with. The goal [...]

By | March 19th, 2019|4G-LTE Optimization Part-1|0 Comments
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