The HX50 modem is a high-performance satellite router designed to support high-speed data links with Quality of Service (QoS) features such as Min/Max CIR together with dynamic allocation of bandwidth.
QoS means that the various types of IP packet are queued up before transmission and sent on in according to a priority order. The objective is to send packets containing time sensitive information, such as fragments of speech in a VoIP call with high priority while, for example, file downloads using ftp are given lower priority.
Min/Max CIR means that for a particular type of traffic (e.g. VoIP packets) that such traffic might be allocated minimum and maximum guaranteed bit rates, for example 83kbit/s minimum and 250 kbit/s maximum. This would allow up to three G711 VoIP calls maximum. Whether a minimum is appropriate is open to debate. Unless you are confident that there is going to be one VoIP call is progress for most of the time then the idea of assigning 83 kbit/s is wasteful and will only cause congestion elsewhere. The problem of setting up these parameters is one of the big difficulties of VSAT traffic management.
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The HX50 modem has several IP features built in including NAT/PAT, DHCP, RIPV1, RIPV2, and DNS server/relay functionality, together with TCP acceleration. The inclusion of a DNS server means that many web page url requests from your LAN will only need to go as far as the satellite modem before finding what IP address the server is located. This will save time downloading from web sites that someone has previously visited. The inclusion of TCP acceleration is a great idea. This will help speed up web page downloads by avoiding repetitive to and fro messaging between your PC and the website. You may wait a few moments longer initially but one the page starts coming you will get the whole lot, text and pictures very quickly.
The modem which encodes and decodes the analogue satellite transmission into data is of advanced design to deal with the new DVB-S2 standard which allows for blocks of higher order modulated symbols using 8-PSK and a variety of FEC rates. The hub knows the receive quality at the remote and adjusts the outlink transmit modulation and coding to match, thus maximising efficiency and minimising costs in the outlink direction. On the return links the modem has several FEC options including modern turbo coding which beats every other FEC system for efficiency, being superior to the older FEC techniques. Turbo coding is now being widely used in many competitive products. The hub knows what is the receive quality from the remote ant is tells the remote to change modulation and coding accordingly, thus maximising efficiency and minimising costs in the return direction.
The HX50 is the ideal platform to enable high-performance IP connectivity for a variety of applications including cellular backhaul, MPLS extension services, virtual leased line services, and other high-bandwidth solutions. Target markets include SCPC/MCPC replacement links, GSM backhaul, MPLS extension services, embassy and government networks and private leased line services.
The HX System is a star network TDM/TDMA VSAT system. Remote HX50 and HX100 VSAT terminals connect via a central VSAT teleport hub.
The outbound carrier from the VSAT hub to all the remotes is a DVB-S/DVB-S2 carrier supporting bit rates up to 121 Mbps. In DVB-S2 the bit rate on the outlink can be varied by altering the number of bits per symbol. The idea is that increases of the bit rate may be possible for large remote terminals or those in the inner contours of the downlink beam and during clear sky conditions. It is not clear in the Hughes HX system if such variable bit rates will occur automatically, improving bit rates during clear sky and reducing them during rain. Overall DVB-S2 will get more bits per second through he satellite for the same price so should result in lower costs to the end user.
Multiple inbound carriers supporting rates up to 3.2 Mbps are possible. The higher return link bit rates will need more transmit power from the remote sites, requiring larger BUC power or larger dish.
Efficiency and flexibility in utilizing the satellite bandwidth have been emphasised in the design. Each link can be configured to provide a QoS tailored for the individual remote terminal. Each remote link can be independently configured with Minimum CIRs and Maximum Rates, thereby allowing a service provider to develop a service tailored to its customers' specific requirements. If this is to work well, the default settings of the QoS parameters must be set sensibly and any tailoring of QoS to suit individual customer's traffic is going to need some careful traffic analysis, determination of parameters and then evaluation to see if the changes have made things better or worse.
The HX System bandwidth allocation scheme uses an Aloha channel for initial traffic requests, which means that remotes can be configured to de-allocate bandwidth based on inactivity. This frees up unused bandwidth and allows an operator to make more efficient use of space segment resources. Because the HX System is DVB-S conformant, the HX System can easily be multiplexed to an existing DVB outbound carrier such as the Hughes HN system, DTH system, or other DVB-based broadband systems.
Quality of Service features include:
On-demand constant bit rate (CBR) services
Minimum CIR with fixed steps to maximum rate (Rate limiting)
Minimum CIR with best effort to maximum rate (Rate limiting)
Best effort services - weighted fair queuing
Class-based weighted prioritization
Multicast data delivery
Four levels of IP traffic prioritization
Supports both pre-assigned (static) traffic assignment and dynamic traffic assignment
Idle remotes can be configured to release all network resources
Static and dynamic addressing, DHCP server or relay
DNS Caching, Full RIPV2 routing support
Multicasts to the LAN by using IGMP
NAT/PAT, VLAN tagging
Firewall support through integrated access control lists
Supports unicast and multicast IP traffic
Software and configuration updates via download from the HX Gateway
Implements dynamic, self-tuning Performance Enhancement Proxy (PEP) software to accelerate the throughput performance by optimizing the TCP transmission over the satellite, delivering superior user experience and link efficiency
Bidirectional data compression
Configuration, status monitoring, and commissioning via the gateway
Embedded Web interface for local status and troubleshooting
Remote terminal management via the Hughes Unified Element Manager and SNMP agent
User-friendly LED display indicating terminal operational status
Closed loop control between hub and remote
Dynamic outbound coding and modulation changes based on received signal
Dynamic inbound coding changes based on received signal
Dynamic remote uplink power control
Two 10/100BaseT Ethernet LAN RJ45 ports
One Serial port (RS-422 or RS-232)
Outbound transmission format: DVB-S or DVB-S2
DVB-S2 supports adaptive coding and modulation
Information Rate (Receive or HX System Outbound Channel): up to 121 Mbps
Information Rate (Transmit or HX Inbound Channel): up to 3.2 Mbps
Symbol Rate (Receive): 1-45 Msps (in 1 Msps steps)
Symbol Rate (Transmit): 128, 256, 512, 1024 ksps
Encoding DVB-S (Receive): Convolutional with concatenated Reed Solomon; Viterbi 7/8, 5/6, 3/4, 2/3, or 1/2
Encoding DVB-S2 (Receive): BCH with LDPC 3/5, 2/3, 3/4, 5/6, 8/9, or 9/10 (8PSK) 1/2, 3/5, 2/3, 4/5, 5/6, 8/9, 9/10 (QPSK)
Transmit encoding: Rate 1/2, 2/3, 4/5 TurboCode, Rate 1/2 Convolutional
Frequency Range: C-. extended C-, Ku-, and Ka-band
Modulation (Receive): QPSK or 8PSK
Modulation (Transmit): OQPSK
Bit Error Rate (Receive): 10E-10 or better
Bit Error Rate (Transmit): 10E-7 or better
1 and 2 watt Ku-band
2 watt C-band
1, 2, and 3 1/2 watt Ka-band
Mass (IDU): 4.8 lbs (2.18 kg) Dimensions (IDU): 11.5" W x 1.8" H x 11" D
(29.21 cm W x 4.7 cm H x 27.94 cm D)
IDU: +32? F (0? C) to +104? F (+40? C)
ODU: -22? F (-30? C) to +131? F (+55? C)
Input power: 90-264 VAC; 50-60 Hz DC power supply (optional): 12-24 VDC
For more information about this new service and to pre-order your terminals for use in the Europe beam of the Eutelsat W3A satellite please click firstname.lastname@example.org for further information on this exciting development.
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Page started 20 June 2007, amended 5 May 2015, 6 Feb 2019 HTML5.