| 1: | What does Shannon's Law state? |
| A1: | Shannon's Law states that error-free transmission is possible as long as the transmitter does not exceed the channel's capacity. |
| 2: | What does the Nyquist sampling theorem state? |
| A2: | The Nyquist theorem states that digital sampling must take place at twice the highest frequency, to reconstruct the analog signal accurately. |
| 3: | What does DMT stand for? How many subchannels does the standard (ANSI) ADSL define? |
| A3: | DMT stands for Discrete Multitone. The standard (ANSI) ADSL system divides the frequency spectrum into 256 subchannels (subcarriers). |
| 4: | Why is CAP modulation sometimes called suppressed QAM? |
| A4: | Because, unlike QAM, CAP is not sending the carrier over the line. |
| 5: | What is the typical speed in the 802.11b standard? What coding techniques provide these speeds? |
| A5: | 1 and 2 Mbps with 11-bit Barker code. 11 and 22 Mbps with Complementary Code Keying (CCK). |
| 6: | How wide is the high carrier in 802.11a; how many subchannels does it have, and how wide is each subchannel? |
| A6: | Each high-speed carrier is 20-MHz wide and is broken up into 52 subchannels, each approximately 300-kHz wide. |
| 7: | How does the 802.11g standard relate to 802.11a and 802.11b? |
| A7: | 802.11g uses the same OFDM technology as 802.11a and operates in the same 2.4-GHz band as 802.11b. |
| 8: | What is the relation between the terms clocking, timing, and synchronization? |
| A8: | Clocking refers to both timing and synchronization. |
| 9: | What interface uses the pseudo-ternary coding technique? What is the size of the frame? |
| A9: | The S/T interface. The size is 48 bits. |
| 10: | What does 2B1Q stand for and which interface does it use? What is the size of the frame? |
| A10: | Two binary one quaternary (2B1Q) over the U-interface. The frame is 240 bits in length. |
| 11: | What is perfect scheduling in the physical layer? |
| A11: | Perfect scheduling is the interaction between the E-bit and D-bit of the frame of the S/T interface that provides a contention mechanism called perfect scheduling. |
| 12: | How do T1 circuits meet the ones density requirements? |
| A12: | By using zero-suppression schemes. |
| 13: | Explain how the 24 framing bits in ESF are broken down and how they are used. |
| A13: | Of the 24 framing bits in an ESF, 6 bits are used for synchronization, 6 bits for error checking, and the remaining 12 bits are used for a 4-kbps facility data link (FDL). |
