![]() ![]() GTP-C is used within the GPRS core network for signaling between gateway GPRS support nodes (GGSN) and serving GPRS support nodes (SGSN). GTP can be decomposed into separate protocols: GTP-C and GTP-U. As we discussed in Chapter 2, in 3GPP architecture, GTP and Proxy Mobile IPv6-based interfaces are specified on various interface points. ![]() The GTP is a group of IP-based transport protocols that are used to carry IP packets within GSM, UMTS, and LTE networks. One GTP tunnel is established for each radio bearer in order to carry user traffic between the eNB and the selected S-GW. The S1-U consists of GTP-U protocol running on top of user datagram protocol (UDP), which provides best-effort data delivery. ![]() The S1-MME is responsible for EPC bearer setup and release procedures, handover signaling, paging, and NAS signaling transport. Each SCTP association between an eNB and an MME can support multiple UEs. The S1-MME carries S1 application protocol (S1-AP) messages, using SCTP 2 over IP to provide guaranteed data delivery. The S1 interface supports a multi-point connection among MMEs/S-GWs and eNBs. The RLC and MAC sublayers both restart in a new cell after the handover.įigure 3.6. Data protection during handover is the responsibility of the PDCP sublayer. In the absence of any centralized control node, data buffering during handover due to user mobility in the E-UTRAN must be performed in the eNB itself. The E-UTRAN user-plane protocol stack is shown in Figure 3.6, consisting of the packet data convergence protocol (PDCP), radio link control (RLC), and medium access control (MAC) sublayers that are terminated in the eNB on the network side. It is the main controlling function in the AS responsible for establishing the radio bearers and configuring all lower layers using RRC signaling between the eNB and the UE. The radio resource control (RRC) protocol is known as layer 3 in the AS protocol stack and in 3GPP RAN terminology. The lower layers perform the same functions as for the user-plane with the exception that there is no header compression function for the control-plane. This includes both access stratum (AS) and NAS protocols. The protocol stack for the control plane between the UE and MME is shown in Figure 3.5. A 3GPP-specific tunneling protocol called GPRS tunneling protocol (GTP) is used over S1 and S5/S8 interfaces. Different tunneling protocols are used across different interfaces. An IP packet for a UE is encapsulated in an EPC-specific protocol and tunneled between the P-GW and the eNB for transmission to the UE. The main functions in each entity and their termination points in the network have been shown in the figure. Landsat 9, like Landsat 8, is both radiometrically and geometrically better than earlier generation Landsats.The functional split between the EPC and E-UTRAN is shown in Figure 3.4. Landsat 9, like Landsat 8, has a higher imaging capacity than past Landsats, allowing more valuable data to be added to the Landsat global land archive-around 1,400 scenes per day. The combined Landsat 8 + Landsat 9 revisit time for data collection with be every 8 days, like it currently is for Landsat 8 + Landsat 7. Landsat 9 replaces Landsat 7 (launched in 1999), taking its place in orbit (8 days out of phase with Landsat 8). ![]() Landsat 9, launched September 27, 2021, joins Landsat 8 in orbit the satellite orbits are 8 days out of phase. Landsat 9 will collect data at the same rate as Landsat 8. Landsat 8 has added more data per year than any proceeding satellite. archive contributed by each Landsat satellite as of Sept. Sustainable Land Imaging Program, Landsat 9 has a design very similar to Landsat 8’s which allowed the Landsat 9 build and launch to be expedited. Since reducing the risk of a Landsat data gap is a high priority of the U.S. Image credit: USGS/NASA More data | Better data Landsat 9 now collects data at the same rate as Landsat 8. ![]()
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