Qualcomm Snapdragon 600 and 800 Processors Specifications

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Qualcomm unveiled two new application processors to power future mobile hardware. Like their predecessors Snapdragon 600 and Snapdragon 800 come with power packed features for fast performance and better battery life.

Qualcomm Snapdragon 600 Features

  • Quad Core Krait 300 CPU running up to 1.7 GHz
  • Adreno 320 GPU – offering over 3x the performance of A225 &, as the first GPU in the Adreno 300 series and introduces support for new mobile and GPGPU compute APIs such as OpenGL ES 3.0 , OpenCL and Renderscript Compute.

  • LPDDR3 RAM— (Low Power Double Data Rate 3)- LPDDR3 RAM will help in increasing the data transmission between different components. With this performance in increased in the processor.

  • Performance Boost—we expect the Snapdragon 600 processor to deliver up to 40% better performance than the Snapdragon S4 Pro processor.

Qualcomm Snapdragon 600 and 800 Processors Specifications

Snapdragon 800 Processors Features

  • Quad Core Krait 400 CPU—speeds up to 2.3 GHz, per core
  • Adreno 330 GPU—featuring patented Flex Render Technology and leading edge API’s that are designed to expand the use of GPU processing for general computing and other SoC tasks, the Adreno 330 GPU offers a 2 times better compute performance than Adreno 320
  • 2x32bit LPDDR3 RAM at 800MHz – with industry-leading memory bandwidth of 12.8GBps.
  • 4G LTE Cat 4 and 802.11ac—these connectivity options offer blazing fast, seamless connectivity with cellular modem boasting data rates up to 150 Mbps and 802.11ac at speeds up to 1 Gbps.
  • UltraHD—video can be captured, played back and displayed in UltraHD (previously called “4K.”) The resolution has four times as many pixels as 1080p. (1920x 1080 versus 4096 × 2304)
  • HD Audio—support for DTS-HD, Dolby Digital Plus and 7.1 surround sound.
  • Dual Image Signal Processors (ISPs) up to 55MP – with support for up to four cameras and allows for 3D captures, photo merging into a master 55MPixel image, separate autofocus and captures, 1080p30 video captures.
  • Overall Performance Boost—the Snapdragon 800 processor is expected to deliver up to 75% better performance than the Snapdragon S4 Pro.

LTE RLC – Radio Link Control Protocol

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RLC is a layer 2 protocol in LTE UE and NodeB. RLC – Radio Link Control protocol is a data link layer protocol. RRC (Radio Resource Control) is generally controls RLC configuration via RRC-RLC SAP. A RLC entity receives/delivers RLC SDUs from/to upper layer and ends/receives RLC PDUs to/from its peer RLC entity via lower layers.

If RLC entity configured at the eNB, there is a peer RLC entity configured at the UE and vice versa.

3GPP LTE RLC UE and NodeB Stack

An RLC entity can be configured to perform data transfer in one of the following three modes:

Transparent Mode (TM)

A RLC TM entity is with can be transmitter or receiver. That means when acting as a transmitter the transparent mode RLC entity receives SDUs from upper layer and transmit those to it’s peer RLC TM entity via lower layer.

Similarly the receiving RLC TM entity receives RLC PDUs via lower layer and then pass those to upper layer.

When RLC TM entity acts as a transmitter

  • It should not segment or concatenate the RLC SDUs
  • No header will be included in TMD PDUs

Unacknowledged Mode (UM)

Similar to RLC TM entity RLC UM entity also acts either as a transmitter or receiver. The transmitting RLC UM entity receives SDPs from upper layer and send RLC PDUs to its peer receiving entity via lower layers. Similarly the receiving RLC entity receives RLC PDUs from lower layer and delivers RLC SDUs to upper layer.

Acknowledged Mode (AM)

AM RLC entity can be configured to deliver/receive RLC PDUs through DL/UL DCCH and DL/UL DTCH logical channels.

When the transmitting side of an AM RLC entity forms AMD PDUs from RLC SDUs, it shall:

  • segment and/or concatenate the RLC SDUs so that the AMD PDUs fit within the total size of RLC PDU(s) indicated by lower layer at the particular transmission opportunity notified by lower layer.

The transmitting side of an AM RLC entity supports retransmission of RLC data PDUs (ARQ):

  • if the RLC data PDU to be retransmitted does not fit within the total size of RLC PDU(s) indicated by lower layer at the particular transmission opportunity notified by lower layer, the AM RLC entity can re-segment the RLC data PDU into AMD PDU segments;
  • the number of re-segmentation is not limited.

When the transmitting side of an AM RLC entity forms AMD PDUs from RLC SDUs received from upper layer or AMD PDU segments from RLC data PDUs to be retransmitted, it shall:

  • include relevant RLC headers in the RLC data PDU.

When the receiving side of an AM RLC entity receives RLC data PDUs, it shall:

  • detect whether or not the RLC data PDUs have been received in duplication, and discard duplicated RLC data PDUs;
  • reorder the RLC data PDUs if they are received out of sequence;
  • detect the loss of RLC data PDUs at lower layers and request retransmissions to its peer AM RLC entity;
  • reassemble RLC SDUs from the reordered RLC data PDUs and deliver the RLC SDUs to upper layer in sequence.

At the time of RLC re-establishment, the receiving side of an AM RLC entity shall:

  • if possible, reassemble RLC SDUs from the RLC data PDUs that are received out of sequence and deliver them to upper layer;
  • discard any remaining RLC data PDUs that could not be reassembled into RLC SDUs;
  • initialize relevant state variables and stop relevant timers.

RLC Functions

  • transfer of upper layer PDUs;
  • error correction through ARQ (only for AM data transfer);
  • concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer);
  • re-segmentation of RLC data PDUs (only for AM data transfer);
  • reordering of RLC data PDUs (only for UM and AM data transfer);
  • duplicate detection (only for UM and AM data transfer);
  • RLC SDU discard (only for UM and AM data transfer);
  • RLC re-establishment;
  • Protocol error detection (only for AM data transfer).

 

RLC PDU (Protocol Data Unit)

RLC PDUs can be categorized into RLC data PDUs and RLC control PDUs.

  • RLC data PDUs are used by TM, UM and AM RLC entities to transfer upper layer PDUs (i.e. RLC SDUs).
  • RLC control PDUs are used by AM RLC entity to perform ARQ procedures.

I added tutorials on encoding and decoding of RLC TM and UM PDUs in earlier tutorials.

LTE RSRP – Reference Signal Received Power

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What is RSRP (Reference Signal Received Power ) in LTE? When RSRP is is applicable in LTE systems?

Reference signal received power (RSRP), is defined as the linear average over the power contributions of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth.

For RSRP determination the cell-specific reference signals R0 shall be used. If the UE can reliably detect that R1 is available it may use R1 in addition to R0 to determine RSRP.

The reference point for the RSRP shall be the antenna connector of the UE. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRP of any of the individual diversity branches.

LTE Cell-specific reference signals

Mapping of downlink reference signals

When is RSRP (Reference Signal Received Power) applicable?

RSRP is applicable in the following cases

  • RRC_IDLE intra-frequency
  • RRC_IDLE inter-frequency
  • RRC_CONNECTED intra-frequency
  • RRC_CONNECTED inter-frequency

The number of resource elements within the considered measurement frequency bandwidth and within the measurement period that are used by the UE to determine RSRP is left up to the UE implementation with the limitation that corresponding measurement accuracy requirements have to be fulfilled.

The power per resource element is determined from the energy received during the useful part of the symbol, excluding the CP.

LTE RSCP – Received Signal Code Power

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What is RSCP (Received Signal Code Power) in LTE? When is RSCP applicable in LTE system?

UTRA FDD CPICH RSCP

RSCP (Received Signal Code Power), the received power on one code measured on the Primary CPICH. The reference point for the RSCP shall be the antenna connector of the UE. If Tx diversity is applied on the Primary CPICH the received code power from each antenna shall be separately measured and summed together to a total received code power on the Primary CPICH. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding CPICH RSCP of any of the individual receive antenna branches.

UTRA TDD P-CCPCH RSCP

Received Signal Code Power, the received power on P-CCPCH of a neighbour UTRA TDD cell.
The reference point for the RSCP shall be the antenna connector of the UE.

RSCP is only valid in UTRA cells and used during RRC_IDLE Inter-RAT or RRC_CONNECTED Inter-Rat state, i.e during LTE to UMTS reselection or handover.

LTE Paging Explained

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How does paging in LTE work? What are the different situations when LTE UE receives paging from network?

Paging in LTE network is used to inform and notify UE about various events. The propose of paging procedure is:

  • To transmit paging information to a UE in RRC_IDLE state.
  • To inform UEs in RRC_IDLE and UEs in RRC_CONNECTED state about a system information change.
  • To inform UE about ETWS primary notification and ETWS secondary notification.
  • To inform CMAS notification.

When RRC layer receives paging it notify upper layer about this. Upper layer may request RRC to establish RRC connection as a response of paging.

How Paging Channel (PCH) is selected in LTE?

System information block type 5 or 5bis (SIB 5 or SIB 5bis) defines all common channels used in idle mode. In one cell one or several PCH channels can be established.

Each SCCPCH (Secondary Common Control Physical Channel) indicated to the UE in system information can carry on PCH. For each defined PCH there is also a uniquely associated PICH.

If more than one PCH,PICH combination is defined in SIB 5 or SIB 5bis, UE should choose the correct one according the following formula:

UE shall select a SCCPCH from the ones listed in SIB 5 or SIB 5bis based on IMSI as follows:

“Index of selected SCCPCH” = IMSI mod K,

Where:

  • K: The number of listed SCCPCHs which carry a PCH. These SCCPCHs shall be indexed in the order of their occurrence in SIB 5 or SIB 5bis from 0 to K-1.
  • IMSI (GSM-MAP)” is given as sequence of digits of type Integer(0..9), IMSI shall in the formula above be interpreted as a decimal integer number, where the first digit given in the sequence represents the highest order digit.
  • IMSI (DS-41)” is given as octet string, IMSI shall in the formulae above correspond to the decoded decimal representation of the IMSI-S part included in the octet string.

If the UE has no IMSI, for instance when making an emergency call without USIM, the UE shall use as default number IMSI = 0.

Actions by UE after receiving paging message

  • If UE receives paging in RRC_IDLE state if UE Identity included in the paging record matches with UE identities assigned by upper layer then UE RRC (Radio Resource Control) needs to forward ue-Identity and cn-Identity to upper layer.
  • If UE receives paging with request to modify system information (systemInfoModification) then reacquire the required system information.
  • If UE is ETWS capable and received etws-Indication in paging message, UE needs to re-acquire SIB 1 immediately. If schedulingInfoLost IE indicates that SIB 10 is present then RRC will acquire SIB 10 otherwise if SIB 11 is present then RRC will read SIB 11.
  • Similarly when smas-Indication is included in paging message, RRC will re-acquire SIB 1 immediately. If schedulingInfoList indicates that SIB 12 is present then RRC layer will acquire SIB 12.

LTE MAC Header Structure

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How LTE MAC header is encoded? What are different header elements in LTE MAC header?

LTE MAC PDU is a bit string but octet aligned (i.e multiple of 8 bits). A MAC PDU header consists of one or more subheaders. Each subheader corresponds to either a MAC SDU, MAC control element or padding.

MAC PDU header can have these six elements R/R/E/LCID/F/L. The last subheader in MAC PDU and subheaders for MAC control elements consists solely of four elements R/R/E/LCID. A MAC PDU subheader corresponding to padding consists of the four header fields R/R/E/LCID.

Here are some of the guidelines followed when multiple subheaders need to be present in a single MAC PDU

  • MAC PDU subheaders have the same order as MAC SDUs, MAC control elements and padding
  • MAC control elements always placed before MAC SDU.
  • Padding occurs at the end of MAC PDU except when single byte or two bytes padding required. When single-byte or two-byte padding is required, one or two MAC PDU subheaders corresponding to padding are placed at the beginning of the MAC PDU before any other MAC PDU subheader.

A maximum of one MAC PDU can be transmitted per TB per UE. A maximum of one MCH MAC PDU can be transmitted per TTI.

LTE MAC PDU Structure

Cell Selection Criteria in 3G UMTS

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What is cell selection? What is the criteria for cell selection?

UMTS

After selecting a PLMN UE need to select a cell to obtain normal or emergency service. Cell selection procedure is divided into two types

  • Initial cell selection : When UE does not have any prior knowledge about RF channels in UTRA band or
  • Stored information cell selection: This procedure requires stored information of carrier frequencies and optionally also information on cell parameters, e.g. scrambling codes, from previously received measurement control information elements.

Cell Selection Criteria

Cell selection criteria S is fulfilled when

  • for FDD cells: Srxlev > 0 AND Squal > 0
  • for TDD cells: Srxlev > 0

How Squal and Srxlev calculated

Squal = Qqualmeas – (Qqualmin + QqualminOffset)

Srxlev = Qrxlevmeas – (Qrxlevmin + QrxlevminOffset) – Pcompensation

Squal Cell Selection quality value (dB). Applicable only for FDD cells.
Srxlev Cell Selection RX level value (dB)
Qqualmeas Measured cell quality value. The quality of the received signal expressed in CPICH Ec/N0 (dB) for FDD cells. CPICH Ec/N0 shall be averaged. Applicable onlyfor FDD cells.
Qrxlevmeas Measured cell RX level value. This is received signal, CPICH RSCP for FDD cells (dBm) and P-CCPCH RSCP for TDD cells (dBm).
Qqualmin Minimum required quality level in the cell (dB). Applicable only for FDD cells.
QqualminOffset Offset to the signalled Qqualmin taken into account in the Squal evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN
Pcompensation max(UE_TXPWR_MAX_RACH – P_MAX, 0) (dB)
UE_TXPWR_MAX_RACH Maximum TX power level an UE may use when accessing the cell on RACH (read in system information) (dBm)
P_MAX Maximum RF output power of the UE (dBm)