Receive flicker-free TV via IPTV

Innovative functions for interference-free IPTV reception

Network TV, also known as IPTV, is the third service in addition to the voice (VoIP) and data services provided to users in the triple play application. About 80% of existing IPTV users access through xDSL, so ADSL2 + is the preferred IPTV operating platform at this stage. Despite the higher bandwidth of VDSL2, ADSL2 + has two obvious advantages of wider coverage and lower cost. It can be predicted that these two xDSL technologies will continue to be used for IPTV in the next few years and will complement each other. Because xDSL uses conventional copper wire transmission, and the transmission medium of copper wire itself is susceptible to interference, IPTV is sometimes affected. Now, there are innovative technologies that can achieve interference-free IPTV reception.

For services such as data transmission and video-on-demand or Internet telephony, the interference on DSL is usually negligible, but due to the real-time nature of the video stream, the interference on DSL may cause problems for IPTV applications. Moreover, there is usually not enough time to implement the correction, which is required by the conventional protection mechanism of the transport layer (such as TCP / IP). If the errors that occur during transmission are not corrected in time, the result will be unbearable image distortion. As shown in Figure 1, in addition to increasing the interleaving depth or RFI suppression and other techniques used to improve anti-interference, erasure decoding and gamma layer retransmission techniques can also be used to eliminate IPTV image problems.

The erasure decoding technology can improve the impulse noise immunity without changing the DSLAM carrier equipment. In practical applications, its error protection capability is twice that of CPE without erasure decoding. Therefore, in any actual installation environment, the use of erasure decoding technology can immediately achieve significant improvements. Gamma layer retransmission mechanism combined with the central office (CO) equipment, using intelligent traffic shaping and differentiation algorithms, can optimize real-time services such as IPTV, VoIP, or online games, and ensure the best service by setting minimum delay and maximum error prediction quality. Even if you use multiple services at the same time, you can ensure the best service quality.

Figure 1 The combination of erasure decoding and gamma layer retransmission technology eliminates the IPTV image problem

Erase decoding For the erase decoding (ED) function, the receiver monitors the ongoing error correction. It can distinguish the error correction measures used by the RS (Lead Solomon) decoder and infer the type of interference based on it. Since the subsequent data blocks are likely to be subject to similar interference, the receiver can “actively” predict the types of data packets that may be interfered, and can take the initiative to adjust these abnormal conditions in an intelligent manner. By erasing and decoding, the impulse noise immunity of CPE can be doubled at most.

However, if the impulsive noise lasts longer than a certain critical value, then erasure decoding can no longer correct all errors, or image distortion may occur. In order to avoid affecting the market acceptance of IPTV, Internet service providers and network operators cannot allow services with quality defects, which is why there is a huge demand for solutions that can provide comprehensive error protection. Gamma layer retransmission (GLR) provides another interesting method.

Gamma layer retransmission The gamma layer refers to the lowest physical layer that distinguishes IPTV from other services. This layer can inform CPE or CO whether a certain data packet is voice or video. Unlike this, the so-called alpha layer retransmission retransmits every lost packet regardless of its service category. However, the retransmission solution will cause additional transmission delays, so it is particularly important to ensure that the mechanism is only used for IPTV and will not affect other services that rely on extremely short runtimes such as VoIP.

GLR can monitor the noise at the transmission layer close to the physical hardware, so that the receiver can respond in time and require the transmitter to retransmit. If the fast retransmission can be successfully completed, the image can generally be refreshed quickly to avoid image distortion. Of course, to achieve this, GLR must be supported by both DSLAM and CPE.

From the above information, we may conclude that using ED and GLR together may be the best way to achieve stable and interference-free IPTV. However, this solution is extremely complex. It not only requires the computer to have quite powerful capabilities, but also needs to use these noise suppression technologies to upgrade the installed basic equipment while avoiding excessive workload or excessive costs .

Single chip solution for ADSL gateway with integrated ED and GLR functions -G306 and other next-generation three-in-one home gateway solutions.

XWAY ARX168 is an ADSL2 + single-chip product that supports Gigabit Ethernet, has the special functions required by IPTV, and supports wireless data transmission rates of more than 150Mb / s (WLAN 802.11n). ARX168 uses innovative noise immunity functions for media services such as IPTV, such as gamma layer retransmission, erasure decoding, and increased interleaving depth, to provide end users with a better service experience, as shown in Figure 2.

Figure 2 XWAY ARX168 has features specifically for IPTV

Figure 3 XWAY ARX168 structure diagram

The integrated Gigabit Ethernet switch works well with the network processor, allowing different bridges and routing services to be flexibly combined without unduly increasing the burden on the application CPU. Two USB 2.0 interfaces provide the convenience of connection for all general peripherals. With the digitization of media formats, the number and capacity of files that end users need to manage has increased significantly. The integrated Gigabit Ethernet switch and the data transmission rate of more than 150Mb / s through WLAN provide the best support for this. As shown in Figure 3, other fast interfaces also include: SPI with DMA support, dual UART (including RS-232) and PCI interface.