Defense Event Capacity, Error Exponent, and Structural Results for Communication Networks Mohsen Heidari Wednesday, December 12, 2018 10:00am - 12:00pm EECS 1200 About the Event Abstract: In various multi-terminal communication scenarios, contrary to point-to-point communication, characterization of fundamental limits such as capacity and error exponent is still an open problem. We study such fundamental limits and the structure of optimality achieving codes. This thesis consists of two parts: in the first part, we investigate the role of algebraic structures in multi-terminal communications. We show the necessity of various types of algebraic structure in capacity achieving codes and argue that the lack of such structures in the conventional random codes leads to their sub-optimality. We develop a new class of partially structured codes called quasi-structured code (QSC). Such codes span the spectrum from completely structured to completely unstructured codes. It is shown that the application of QSCs leads to improvements over the current coding strategies for many problems including distributed source coding and multiple-access channel (MAC) with feedback.
In the second part of the thesis, we study the optimal error exponent in various multi-terminal communication scenarios. We derive a lower and upper bound on the error exponent of discrete memoryless MAC with noiseless feedback and variable-length codes (VLCs).
The bounds increase linearly with respect to a specific Euclidean distance measure defined between the transmission rate pair and the capacity boundary. The bounds are shown to be tight for specific classes of MACs.
- Attaining maximal reliability with minimal feedback via joint channel-code and hash-function design Stark C. Draper †, Kannan Ramchandran, Bixio Rimoldi‡, Anant Sahai †, and David N. Tse † Department of EECS, University of California, Berkeley, CA, USA ‡ Mobile Communications Laboratory, EPFL, Lausanne, Switzerland.
- Apr 30, 2004 - Motivation; Background: error exponents for single-user channels. Gaussian MAC (Gallager85; Guess&Varanasi00); Wireless MIMO MAC at high SNR (Zheng&Tse03). Joint Maximum-Likelihood (ML) decoding. Where Esu (R,SNR) is any error exponent upper bound for the AWGN channel.
In addition, the x-ray tomograms provide quantitative data from the cell architecture. Therefore, nanoscale soft x-ray tomography is a new valuable tool for numerous qualitative and quantitative applications in plant cell biology.
Additional Information Sponsor(s): Professor Sandeep Pradhan Open to: Public.
Has anyone experienced any issues resetting (AD) passwords on a Mac? In AD I select an account and set, “User must change password at next login”, I attempt to login as that user and am prompted to change the password, but all password entered are rejected with: Your password does not meet the requirements of the server.” The password policy is set to 8 characters and that’s it. This same user will have no issue resetting in Windows. I will also receive the same error when attempting to reset from Users & Groups in System Preferences. I have seen this many times in the past so I don’t believe it to be strictly related to Mavericks, Yosemite or in this test case, Sierra.
Upper Bound On The Error
What’s strange is that some users will reset just fine. It would be great if I could resolve this as all of our student passwords are reset come deployment, requiring them to change it when they’re picked up.
When we run into this problem we usually just change it in AD manually for them. Password changes for AD users on MacOS (AD-bound Macs) are anything but trouble-free, in my experience. Wireless-only/mostly Macs and FileVault encryption add to the complexity. As far as I know, MacOS supports either machine OR user authentication, but does not support machine authentication with user 're-authentication' (upon user login). See I think this adds to the potential for password change problems in an AD environment. Let's say the AD password expires for a Mac user (mobile account; allows sign on when working 'offline'/remotely) with no wired connection.
Let's also assume their wireless config is setup manually in their user profile, or by user-targeted profile (e.g. Via Profile Manager).
With no network connection, they can sign on MacOS using their old/expired AD credentials. When they connect to wireless / authenticate to the network, they are informed their password has expired and prompted to change it. In this scenario, the AD password generally updates successfully, assuming the new password meets any enforced requirements. So you sign off or shutdown and next time you boot/sign on your Mac, it won't accept the new password.
What happened? Your AD password was updated successfully, but in the presented scenario, the credentials cached in your user profile on the Mac were not updated. With no network connection before sign on, you're authenticating against the cached credentials, not against AD. To correct this: 1.
Sign on with the old password (preferably, do this before signing off or shutting down, after an AD password change). Connect to your wireless network-it's important your Mac can reach an AD domain controller at this point. Open Terminal from Applications Utilities. At the prompt, enter su -l username (where username is your AD username).
You will be prompted to enter your password. Enter your new/current AD password.
Assuming a domain controller is reachable, your password will be accepted, and your cached credentials updated. Terminal will offer little feedback upon success. You should see no error indicating an incorrect password, and a new/second prompt in the Terminal window. Quit Terminal. If you sign off (or shutdown/restart) now, you can sign on your Mac with your current AD password. When you next sign on, you should see a prompt indicating your Login Keychain password doesn't match your account password, and will be prompted for the Login Keychain password, to update the Login Keychain password. Enter your old/previous AD password.
At this point, your AD password, cached credentials in your profile and Login Keychain password should match. Add FileVault encryption to the mix, and you have yet another layer where credentials may be out of sync, so you may need to enter an old password when you first power on your Mac, then enter a different password at a 'proper' MacOS login screen. My understanding is that booting your Mac with a network connection (reachable AD domain controller; borrow/steal a colleagues USB/thunderbolt wired network adapter, or convince your admin to deploy system-targeted profile with machine authentication for wireless?) and entering your current AD password, will update the credentials for FileVault. On top of all this, even 'normal' password expiration/change scenarios (wired connections) have been troubled, for us. The problem(s) may be with our environment. For example, a user with expired AD password comes to the office and docks his Mac (dock provides wired connectivity). When the user attempts to sign on, they're informed their password has expired and prompted for a new password.
When they enter/confirm a new password, the box 'shakes', indicating something was off. I (admin) even tried changing it, to make sure password requirements are met. Rebooting seems to resolve the problem sometimes. For what it's worth and hopefully it helps someone. Have you guys managed to resolve this entirely?
These issues keep repeating themselves, and I'd love to hear what solutions you've found for the issue - systemwide If you have any kind of solution that I could look into and use, that would be really helpful for me. My simplest solution is change the password once when asked by the expired procedure during login (you will get the complexity error) just click cancel ( as mentioned AD actually accepted the password change) login again with the new password, and you'll get in (of course there will be the issue with keychain - couldn't figure that one out, as my users keep getting many pop ups of the what seems to be the same keychain.) So, any help would be appreciated, thanks everyone! Hi all, reviving this post again as it is a major issue for me too. have you found any stable valid fix for this? Regarding the Mac not accepting password change when having an expired password moment, we named it 'the mac dance' 1. You enter your current password and reach the change password window (usually computer is on standby, so passed the file vault authentication, and connected wirelessly to the network where the domain is reachable. In the change password window type the old and new passwords as usual 3.
You will get the screen shake of something wrong, just ignore it and click cancel to go back to choosing to login with whatever user is available. Give it like a few seconds (at least in our environment) and choose your user again and enter the new password, It'll let you login, but will get that annoying keychain issue. Is there a way to correct it?
Or bypass that issue? Edit Sorry for double post - mistook the moderation process as message not sent. Leaving both on should there be extra info on one of them. I'm sure this isn't the case with everyone else but wanted to throw this in just in case someone is having a related issue with this error message as it had nothing to do with a password requirement (letters, numbers, etc.). The problem could be because your AD environment is set to not allow users to change their password after X number of days. Check the 'Minimum password age' in Group Policy.
When you try to use 'kpasswd' in Terminal we got the message 'Soft error:'. This error kept appearing for us after a user changes their password and then tries to change it again in System Preferences Users & Groups.
Come to find out we have the 'Minimum password age' set in Group Policy. We waited the minimum days and the password change went through successfully.